Problems with memory and CPU, is one of the greatest concern of computer enthusiasts. How to match? Hundreds of articles on the Internet, to see dazzling, if not carefully analyze and judge, it is difficult to distinguish which is correct, which is wrong. According to my analysis, the formation of this situation for several reasons: First, the CPU FSB, with the front-side bus frequency is often mixed, and sometimes also the front-side bus with HT bus can also be confused; three kinds of memory (SDRAM, DDR1 SDRAM DDR2 SDRAM) characteristics,
but is often confused with, mix; with a frequency of various names, various names are often mixed; four Intel CPU and AMD CPU features, mix them with the memory is not the same, but is often confused with; five before AMD K8 CPU K8 and CPU features, is often confused with; memory settings for the various motherboard manufacturers often use different methods and name, easy to make people confused; seven is the age of article writing is not specified, do not know which age, what type of memory; (8) is to write the author's level uneven, cohabitation is sometimes difficult to distinguish right and wrong . Therefore, in the study of memory, knowledge, and I really spend a lot of time. See much more, want more, of course, also the initiation of some personal opinion. In order to consolidate the results of my study, I have made this summary memo. Of course, want to give the same "rookie" netizens by reference, and we welcome the "heroes" were corrected.
The concept of CPU frequency
CPU frequency is the speed of your computer, we often say is very important. However, the CPU itself is just a chip, does not produce frequency, frequency computer motherboard plus to it. Its frequency is the frequency that it is functional, if the frequency is too high, that is it for the use of excessive overclocking, it will "strike" or even burned. CPU frequency is equal to the FSB (CPU Host Frequency) multiplied by the multiplier (Multiplier),
Frequency = FSB × multiplier
In fact, the multiplier is not the frequency, just a multiple of the frequency multiplier is set in the CPU. The FSB is the frequency of the generator in the computer's motherboard is the computer's clock standard, also known as the system clock frequency. For example, a CPU multiplier ratio is 10, plus its FSB is 200 MHz, the CPU clock speed is equivalent to
200 MHz x 10 = 2000 MHz = 2.0 GHz
(2) front side bus concept
Front Side Bus (FSB) CPU with the motherboard's North Bridge (North Bridge) linked to the bus, it is the frequency that the CPU and the outside world (memory, AGP bus, PCI bus, etc.) the speed of data transmission. Before the advent of the Pentium 4, FSB frequency and FSB is the same. However, as computer technology continues to evolve, it is found that the front side bus frequency higher than the FSB Therefore, the front-side bus with FSB different. On the Intel platform, the front side bus frequency is four times that of the FSB; in the AMD platform, the front-side bus frequency of 2 times the FSB. Since the emergence of AMD K8, AMD has memory controller integrated in the CPU's internal links between the CPU and memory no longer through the FSB and North Bridge of the front-side bus no longer exists. However, the Intel platform, the front-side bus still exists.
Nevertheless, it is still often the front-side bus with FSB confused with, until now.
(3) a variety of memory frequency name Discrimination
Online, and even the motherboard manual to the CPU-Z, is called a variety of computers of various frequencies far from uniform, so probably comb:
Core frequency (Core Frequency): also known as the memory of the true frequency or limit frequency refers to the memory chips capable of withstanding the limits of frequency, if added to its frequency over this figure more (memory over OC), it will refuse to work. The most common reaction is "blue screen".
Clock frequency (Clock Frequency): refers to the actual operating frequency of the memory. The title of this frequency, for example, the frequency of memory, the operating frequency, operating frequency, bus frequency, DRAM frequency. In Hong Kong and Taiwan said it was too veins. Known as "speed" on many occasions also frequency.
The data frequency (Date Frequency), also known as the equivalent frequency or transmit frequency.
The three names in order not to cause confusion, memory frequency to retain only the core frequency, clock frequency and data frequency. However, some will not lead to misunderstanding, and appropriate to the occasion and the theme will clock frequency is called the operating frequency, operating frequency and bus frequency.
4 classes and attributes of the memory
For the average user, memory, three types: SDRAM memory, DDR SDRAM memory (also known as DDR or DDR1) and DDR2 SDRAM (referred to as DDR2). DDR3 memory soon after, not yet widely used.
SDRAM (synchronous dynamic random access memory), the DRAM Synchronous, said it was "synchronous dynamic random access memory" means that the speed of its work is synchronized with the system bus speed, which in one clock cycle only at the rising edge of the transmission
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times the data, this memory core frequency (Core frequency), the clock frequency (Clock freq.) and data frequency (Data freq.) is consistent.
DDR SDRAM stands for Double Data Rate SDRAM is the meaning of double data rate synchronous dynamic random access memory, DDR memory is evolved on the basis of SDRAM memory, it can be a data clock rise and fall of each transmission, therefore , its clock frequency and core frequency is equal, but its data frequency is doubled Fan of. That the core frequency, memory clock frequency and data frequency of three 1:1:2 relationship.
DDR2 DDR memory on the basis of the data off than DDR, use of special techniques that can be handled than doubled. That is, did the memory core frequency, clock frequency and data rate among the ratio 1:2:4.
The relationship between the frequency characteristics of the three kinds of memory and a few frequencies as follows:
Table 1 three memory frequency relationship
SDRAM, DDR1 and DDR2-400 already has been eliminated, however, in the old computer, the memory of the three specifications is still exist. For example, in 2002, I purchased IBM Black Edition, was considered more advanced, but its memory is SDRAM, capacity is only 128MB. Upgrading the speed of the computer is really fast.
5.Intel platform memory and CPU synchronization conditions
In order to ensure memory safety at work, add to the frequency of the memory can not be too high; in order to ensure the speed of your computer, plus the memory frequency should match with the CPU speed, not too low, therefore the memory requirements for synchronization (Synchronize), memory synchronization? There are various versions of the Internet, some said: "The memory frequency is equal to the FSB is the memory synchronization; Some said:" equal to the memory clock frequency and FSB is the memory synchronous. For example, when the FSB is 133 MHz, the motherboard supports SDRAM, it should be accompanied by PC133 memory; motherboard supports DDR1, together with a DDR 266 memory. These claims are of course correct.
However, for DDR2 memory, if I am: on the Intel platform, equal to the memory clock frequency and FSB is the memory synchronous "have a problem. For example, for the FSB = 800 MHz CPU, FSB equal to 200 MHz in this case, together with the DDR2-800 is the synchronization. This is not the memory clock frequency equal to the FSB ", but the memory clock frequency is equal to twice the FSB is the memory synchronous. So, I think, DDR2 memory is also included, it should be synchronized conditions to the memory core frequency is equal to the FSB synchronous memory "is accurate.
Of course, can also be separated from DDR2 with SDRAM, DDR, such as can say: "When the choice of DDR2 memory, FSB and memory clock frequency ratio of 1:2, that is, memory synchronization.
Example 1. Intel production of the CPU FSB is 200 MHz, if equipped with DDR memory, should be equipped with what type of memory is the memory synchronous?
A: For DDR memory, the core frequency is equal to the FSB memory synchronization, the core frequency is 200 MHz memory is DDR400, DDR400 memory should choose. Of course, said: "DDR memory, the clock frequency is equal to FSB memory synchronization when the FSB is 200MHz, DDR400 memory, we should choose."
Cases. Intel production of the CPU FSB is 200 MHz with DDR2 memory, should be equipped with what type of memory is the memory synchronous?
A: DDR2 memory, the core frequency is equal to the FSB memory synchronization, the core frequency is 200MHz, the memory is DDR2-800, should choose DDR800 memory. Of course, you can say: "DDR2 memory, FSB clock frequency ratio of 1:2 is the memory synchronous, therefore, when the FSB is 200 Mhz, select the DDR800 memory, because the DDR2-800 memory clock frequency is 400MHz with the FSB is a 1:2 relationship. "
The table below, listed in the different FSB conditions, how to select the memory. Single-frequency synchronization point of view, remove the table "dual DDR" in the "double" word is also a memory synchronization.
Table 2 memory reasonable matching table
Note: DDR memory slots with DDR2 memory slot is not the same, you should choose what memory to the motherboard.
6. The FSB bandwidth and memory bandwidth to match the conditions
When the select memory, in addition to the synchronization requirements of the memory, there is an important condition is the requirement of memory bandwidth and front-side bus (FSB) bandwidth equal to the best. If memory bandwidth is less than the bandwidth of the FSB, the CPU wait time will increase; if the memory bandwidth is greater than the FSB, the formation of a waste of memory resources.
For platforms that support DDR1, if the FSB is 200 MHz, single-memory synchronization point using a DDR400 can, however, because the FSB frequency is four times the FSB is 800 MHz, the bandwidth of 800 MHz x 64b ÷ 8b / B = 6.4 GB / s, the bandwidth of DDR400 is only 3.2 GB / s. Therefore, in order to match the memory bandwidth with the bandwidth of the FSB, it should be added to the same memory DDR400 up dual channel operation.
The platform supports DDR2, if the FSB is 200MHz, as long as with a DDR2-800, both to meet the memory synchronization requirements, but also meet the matching requirements of bandwidth.
The bandwidth of the matching conditions, can calculate the bandwidth method to determine, from the perspective of frequency, as long as the memory data frequency is equal to the frequency of the FSB is the bandwidth matches. For example, the data frequency of DDR2-800 dual channel DDR400 800 MHz FSB frequency of 800 MHz, so with the best mix.
In short, if added to the memory frequency is too high, the consequences of the "blue screen" or computer unstable; add to the memory frequency is too low, is a waste of resources of computer frequency. Bandwidth does not match the consequences of a waste of resources. Meets the memory synchronization, but also to meet the bandwidth matching, is the memory and the CPU with.
7. Intel platform memory asynchronous setting method
What is the memory asynchronously? In order to achieve some kind of memory work with the FSB frequency, referred to as memory asynchronous (Asynchronize),. The so-called memory and CPU with how to adapt to changes in CPU frequency is actually the memory frequency. For example, when the computer's CPU FSB from 166 MHz overclocked to 200 MHz, the added memory frequency will follow the upgrade to 200 MHz, so that memory can continue to work? The
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sole coated tip Yue Mei deceive play the occasion of the frightened rural the acyl Gu the carbuncle deceive Xian sodium Germany to decorated ? 66 MHz, unchanged, or only small changes. When the memory frequency is higher than the frequency of the CPU, is generally not subject to specialized settings, because the memory frequency are backward compatible. However, if you want to make this memory in the higher frequency operation, but also can be used for asynchronous memory settings so that the memory work at higher frequencies, to achieve the best use.
Memory asynchronously in the BIOS settings, current motherboard support most of the memory asynchronous technology. Of induction, set the following various, as described below:
⑴ directly regulates the maximum memory frequency increase or decrease - ± 33 MHz of the provisions of the early memory asynchronous technology is to use this solution. For example, when the P3 processor running at 100 MHz FSB through the BIOS settings, memory can be run asynchronously in the two frequencies of 133 MHz or 66 MHz.
⑵ the provisions of sub - which provides that the ratio of the FSB and memory clock frequency, frequency ratio and this ratio is called the divider coefficient (DRAM Frequency Ratio). Divider coefficient setting the value of a variety of different motherboards have different setting values, such as: 1:1 (synchronous), 1: 1.33, 4:3,4:5,5:4,12:13 . Divide factor greater than 1, the memory frequency is less than the FSB; divider coefficient is less than 1:00 is the memory frequency is greater than the FSB. For example, when the FSB is 200 MHz in the BIOS, you choose the sub-frequency coefficient is 5:4, then the memory frequency is 200 MHz x 4 ÷ 5 = 160 MHz, quite DDR320. If you install the memory is DDR333 or DDR2-667, exactly matching (memory frequency is slightly larger, do no harm).
⑶ set the memory multiplier (System Memory Multiplier) - Gigabyte (GIGABYTE) p31 motherboard is set. Multiplier in the BIOS options are: Auto (default actual installed memory on the motherboard), 3.33,3,4 +, 2.5 and 2. When the FSB is 200Mhz actual installed memory is DDR2-800, if you choose multiplier "3.33", then the memory clock frequency (Memory Frequency) will show "800 667", "800" you actually installed on the motherboard DDR2-800; "667" is to tell you: DDR2-667 asynchronous to mean, that is actually running in memory clock frequency is 333 MHz instead of 400 MHz.
⑷ directly - for example, the memory clock frequency (DRAM Frequency) Asustek (ASUS), P5E-VM motherboard BIOS setup options are: Auto, DDR2-667, DDR2-800, DDR2-834, DDR2-888 memory model DDR2-1000 DDR2-1112 and DDR2 = 1333 8 option, you intend to asynchronous memory to what extent, directly corresponding to the model chosen can be simple and straightforward. However, you can only choose within this range.
Example 3. FSB to 200 MHz front side bus frequency is 800 MHz Intel platform motherboard is installed on the DDR2-800 memory, when the FSB overclocked to 250 MHz, memory clock frequency is the number? If you do not want to upgrade the existing memory, how to set the memory asynchronous?
A: From the given conditions, install the DDR2-800 memory to meet the memory synchronization conditions (FSB: Memory clock frequency = 1:2), DDR2-800 memory clock frequency is 400 MHz.
When the FSB to 250MHz, the memory clock frequency synchronization upgrade. The memory clock frequency of 250MHz x 2 = 500MHz, quite of DDR2-1000. Memory overclocking, should upgrade the memory to DDR2-1066 go. If you want to use DDR2-800 memory, and can do the memory asynchronous settings. Gigabyte p31 motherboard, for example as follows:
In the beginning of the boot, click the "Del" key to enter the BIOS → use the up and down arrow keys to select the "MB Intelligent Tweaker (frequency / voltage control)" → Enter and select the "System Memory Multiplier (SPD) memory multiplier adjustment "→ select" 3.33 ", then" Memory Frequency memory clock adjustment "appears" 800 667 "two sets of figures, one of the" 800 "is your actual installed memory DDR2-800;" 667 " is asynchronous memory frequency of DDR2-667, the clock frequency of 333 MHz, DDR2-800 memory can be competent, however, the speed of the corresponding down.
Instructions in the "memory" and "clock" is Hong Kong and Taiwan terms, respectively, the meaning of "memory" and "clock frequency".
8.AMD platform method of calculating the actual memory frequency
On the Intel platform, the memory controller (Memory Controller) is placed within the North Bridge (North Bridge), the memory associated with CPU Front Side Bus (FSB), therefore, we calculate the Intel platform memory frequency above FSB as reference. AMD CPUs (the K8 and beyond) platform, the memory controller is placed within the CPU, so the calculation of the memory frequency of the AMD platform, based on CPU clock speed as a reference. Moreover, in the AMD platform, the asynchronous method of calculating with the synchronization method of calculating any difference.
In the BIOS memory frequency (in the BIOS, the memory frequency commonly used in English DRAM Frequency, Memory Frequency, or the Memory the Clock Frequency) is set to "Auto" or "By SPD", the memory controller will automatically detect your type and parameters of the memory installed on the motherboard, as long as you install the memory the motherboard supports the memory controller for you automatically calculated in the actual operation on the memory frequency, you can wash its hands of it.
If you select the memory core frequency is equal to the CPU FSB (for example, when the FSB is 200Mhz, you use DDR400 or DDR2-800), and this method is set (ie, computer memory frequency is automatically set for you the actual installation. The memory frequency), in fact, is the AMD platform synchronization settings.
However, with the Intel platform, the AMD platform, even if this synchronization settings, and its operating frequency and the nominal value may also vary. For example, you clocked at 2.2GHz, the multiplier is DDR2-800 memory, the installation of the AMD platform 11, the memory operating frequency is not 400MHz, but 366MHz, which is quite DDR2-372 memory. Why is there such a situation, with the special calculation method for the AMD platform, the memory controller design, the following will be introduced.
On the AMD platform, do memory asynchronous set, rarely used the divider ratio that are direct memory model. For example: DDR400,
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DDR2-400, DDR2-533, DDR2-667, DDR2-800, DDR2-1066, DDR2-1333 and so on.
AMD platform, the memory of the actual work is how to calculate? About the steps are as follows:
⑴ set the memory frequency in BIOS: if you actually installed in the memory slots on the memory core frequency is equal to the FSB in the BIOS set the memory frequency to select "Auto" or "By SPD", which means that you do is the memory synchronization settings. However, because the AMD platform, the memory operating frequency is determined by the CPU frequency, so only the memory clock frequency can be divisible by the CPU frequency, memory operating frequency to its nominal frequency is consistent .
It should be clear: you set in the BIOS memory frequency, the same as the actual frequency of memory installed on the motherboard; or may not be the same. If the frequency you set in the BIOS is lower or higher than the frequency of memory actually installed in the memory slot, memory asynchronous set. However, the current DDR2 memory overclocked to allow the limited scope of the current motherboard is mostly higher than the motherboard memory frequency setting options.
⑵ calculate the frequency division factor: First calculate the memory controller automatically sets the frequency division multiple DIV (Divider), often referred to as the divider factor:
DIV = CPU nominal frequency ÷ memory clock settings in the BIOS
If DIV decimal, then it should carry an integer, for example, 7.4 into 8. This is to ensure the safety of memory. Identify unclear whether the binary calculated DIV after the decimal point the number is very small, should take on more of the decimal point of the divisor (eg, 133) a few (for example, take 133.33333), and then the calculator or computer to calculate the DIV, it is easy to discern whether it should be binary.
If the calculated DIV is less than 5, it will be taken as 5. This is an important rule. However, because today's high CPU frequency, so this rule is often ignored.
The calculated value of the DIV is fixed in the memory controller on the CPU inside is not going to change because of the changes in the motherboard.
⑶ calculate the actual memory clock frequency: know the memory frequency division multiple memory clock frequency using the following formula:
The actual memory clock frequency = ÷ memory of the actual frequency of the CPU frequency division multiple
In the calculation, note that the difference between "nominal frequency" and "actual frequency". If you do not overclock, the two are equal.
The calculation results came out, you can determine the memory you choose is appropriate.
Example 4: CPU AMD Athlon (Athlon) 64 3200 +, clocked at 2.0 GHz, FSB is 200 MHz, intended to adopt a DDR400 memory (Auto) setting in the BIOS to do this, ask: (1) sub- The frequency of multiples? ⑵ the actual frequency of the memory?
Solution: (1) because the CPU clock speed is equal to 2000 MHz; DDR400 clock frequency equal to 400MHz / 2 = 200 MHz, memory sub-frequency multiples = 2000 MHz, ÷ 200 MHz = 10;
⑵ in question did not say that overclocking the memory clock frequency = 2000 MHz, ÷ 10 = 200 MHz, the memory is 200 MHz, therefore, to install DDR400 memory is the memory synchronous state.
Example 5. CPU Sempron 3200 +, clocked at 1.8 GHz, motherboard FSB is 200 MHz, the selection of DDR II 800 memory, and asked: (1) divided by a multiple of the number of how many? ⑵ memory clock frequency?
Solution: (1) sub-frequency coefficient DIV = 1800 MHz ÷ 400 MHz = 4.5, should be taken to be 5;
⑵ because the title did not say that overclocking the memory clock frequency = 1800 MHz, ÷ 5 = 360 MHz,. Upcoming memory relegated to DDR2-720. Because of the frequency of the memory is backward-compatible, so, such a configuration is also possible, but also that memory to run in synchronization status.
Example 6. A AMD CPU Nominal frequency is 2.0 GHz, FSB 200 MHz, set the BIOS memory is DDR2-800. FSB super to 250 MHz, and how to select the memory?
Solution: (1) sub-frequency multiples DIV = 2000 MHz ÷ 800 MHz, ÷ 2 = 5.0;
(2) When the FSB to 250MHz, the actual frequency is 250MHz x 10 = 2500 MHz, memory clock frequency = 2500 MHz, ÷ 5 = 500 MHz, this frequency is the clock frequency, it is multiplied by 2 memory The data frequency corresponding to the DDR2-1000. Therefore, in this case, DDR2-800 is overclocking, may make your computer run unstable, and should be replaced as DDR2-1000 memory to do.
If you do not want to replace the now installed on the motherboard, DDR2-800 memory, you can also do the memory asynchronous settings. The BIOS memory frequency is set a little lower, for example, set to DDR2-667, In this way, the DIV = 2000MHz ÷ 333MHz = 6. Overclocked frequency is 250MHz x 10 = 2500 MHz, 2500 MHz, ÷ 6 = 416 MHz memory clock frequency will be, if you now install the DDR2-800 memory physical good, such a small frequency of "overload" , should be can afford, she says.
If you do not worry, the memory frequency in the BIOS setting and then a little lower, for example set to DDR2-533, this time the DIV = 2000MHz ÷ 266MHz = 7.5, should carry is taken as 8. In this way, the clock speed of the CPU overclocked to 2500 MHz, memory clock frequency is 2500 MHz ÷ 8 = as 312.5MHz, quite of DDR2-625, so that you installed on the motherboard, DDR2-800 memory work lightly and more. However, this is in exchange for the sacrifice of memory speed.
The following table is a table calculated in accordance with the above reasoning, it is to explain the relationship between the BIOS set the memory frequency (DRAM the Frequency or Memory Frequency) with the actual memory frequency. Table "divide" we said above, divided by a multiple of the DIV; actual operating frequency of the memory clock frequency, the premise is not overclocked. Table using the The Scarlet Letter, said the sub-frequency and the number of clock frequency, and that calculated from the DIV less than 5, the memory controller into 5.
When overclocking the answer to the above three examples can be directly from the table to check out. However, the overclocking situation in the table divided by the coefficient ("divide") is still available, simply divide it by overclocking frequency to get the memory working frequency. This method has been used in Example 3.
Table 3 in the AMD platform BIOS settings the effect of frequency table
Note: from the table
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seen: clock frequency settings in the BIOS can be evenly divisible by the frequency of the frequency of memory can be to make full use of the frequency (Table in blue bold figures) Otherwise, the memory The frequency will be reduced. This is the setting of the memory controller in order to protect the memory overclocking sake.
Example 8. Frequency in the AMD platform is a 1.6GHz processor multiplier is 8, when the memory frequency is set in the BIOS DDR 333 memory operating frequency is?
A: The DIV = 1600 MHz/166.66 = 9.6, is taken as 10, the memory operating frequency is 1600 MHz ÷ 10 = 160 MHz, quite DDR320. This example: If the memory clock frequency is not divisible by the frequency of the CPU, memory can not be fully synchronized with the CPU.
9 With regard to dual-channel memory technology
Manufacturing CPU technology has improved continuously, the CPU frequency to enhance fast, but the level of technology of manufacturing the memory can not simultaneously improve the speed of the memory is always behind the CPU. For example, in a few years ago, the FSB frequency to 800 MHz and memory frequency has been unable to break through DDR400. Memory synchronization point of view, DDR400 memory with FSB 800 MHz CPU is synchronized. However, from the perspective of bandwidth matching, is not matched. So there was a dual-channel memory technology.
What is dual channel? The dual-channel system includes two independent, complementary smart memory controller, in theory, the two memory controllers are able to simultaneously between zero delay operation. The structural principle of the following figure shown on the right.
Dual channel with memory, when the controller B ready for the next access memory, the controller A read / write main memory, and vice versa. This complementary function of both the memory controller can make the wait time reduced by 50%. Two dual-channel DDR memory controller functionality is exactly the same. Ordinary single-channel memory system with a 64-bit memory controller, dual-channel memory system, there are two 64-bit memory controller, with a 128bit memory in dual channel mode bits wide, so in theory, the memory bandwidth doubled. For example, the single-channel DDR400 bandwidth is 3.2GB / s, if the same memory plus a dual-channel bandwidth into a 6.4GB / s.
Therefore, for the front-side bus is 800 MHz platform with two DDR 400 memory, dual channel, not only to meet the frequency synchronization requirements, but also to meet the matching requirements of bandwidth. However, for DDR2 memory, just with a DDR2-800 memory on it. In doing so, also can satisfy the synchronization requirements, but also to meet the bandwidth requirements. If you want to dual-channel, only to add a DDR2-800 memory. If you want to save a little, when you intend to use two DDR2-400 memory settings for dual channel to cope with 800 MHz FSB, while the bandwidth can meet the requirements, but the FSB is 200MHz, memory clock frequency is 200 MHz, can not meet the installation DDR2 memory FSB and memory clock frequency ratio of 1:2 requirement, therefore, the memory is out of sync, unless you do the memory asynchronous set, otherwise, make the computer unable to stabilize the operation.
However, we often see this argument: "dual-channel with two DDR2-533 memory can be used on the FSB is 1066 MHz platform" sort of argument. I say this is wrong, because each channel are independent, when you set the dual channel can indeed increase the bandwidth, however, the memory clock frequency is not doubled. The following experimental results can be seen: the single-channel, the clock frequency of the memory (DRAM Frequency) 400 MHz, then one is DDR2-800 memory, dual-channel detection, the clock frequency of 400 MHz, and set up a dual-channel double.
By the test results can be seen, the dual-channel memory capacity of 1024 MB expanded to 2048 MB. And indicates that the dual-channel (OC mode) is symmetrical, This means that the bandwidth is doubled Fan of.
Note: "FSB: memory test results" may wish to "FSB: Memory clock frequency," Therefore, the ratio of 1:2, or 200 Mhz: 400 MHz, Does CPU-Z FSB and FSB confuse? !
Older motherboard for dual channel memory requirements more demanding, we must first motherboard chip support, was also requested from the same manufacturer specifications, the same memory capacity installed in the correct way in order to form a dual-channel. However, the current motherboard mostly supports dual channel, and the use of the FMT technology has been greatly reduced, dual-channel memory specifications and capacity requirements, so dual channel is a relatively easy thing to do. However, for more than three memory slots motherboard, if your memory is not exactly the same, the installation must be installed in accordance with the motherboard manual. The principle is the same size of memory of "separated by interpolation or interpolation method for a group of two slots of the same color. Have to look at the motherboard manual to insert before, because there is no uniform standard in this regard, therefore, must be manual shall prevail. .
Check whether dual-channel, you can use special software to check. Such as CPU-Z makes EVEREST, SiSofyware, Sandra and so on.
Memory and CPU matching method
Problems with memory and CPU, is one of the greatest concern of computer enthusiasts. How to match? Hundreds of articles on the Internet, to see dazzling, if not carefully analyze and judge, it is difficult to distinguish which is correct, which is wrong. According to my analysis, the formation of this situation for several reasons: First, the CPU FSB, with the front-side bus frequency is often mixed, and sometimes also the front-side bus with HT bus can also be confused; three kinds of memory (SDRAM, DDR1 SDRAM DDR2 SDRAM) characteristics,
but is often confused with, mix; with a frequency of various names, various names are often mixed; four Intel CPU and AMD CPU features, mix them with the memory is not the same, but is often confused with; five before AMD K8 CPU K8 and CPU features, is often confused with; memory settings for the various motherboard manufacturers often use different methods and name, easy to make people confused; seven is the age of article writing is not specified, do not know which age, what type of memory; (8) is to write the author's level uneven, cohabitation is sometimes difficult to distinguish right and wrong . Therefore, in the study of memory, knowledge, and I really spend a lot of time. See much more, want more, of course, also the initiation of some personal opinion. In order to consolidate the results of my study, I have made this summary memo. Of course, want to give the same "rookie" netizens by reference, and we welcome the "heroes" were corrected.
The concept of CPU frequency
CPU frequency is the speed of your computer, we often say is very important. However, the CPU itself is just a chip, does not produce frequency, frequency computer motherboard plus to it. Its frequency is the frequency that it is functional, if the frequency is too high, that is it for the use of excessive overclocking, it will "strike" or even burned. CPU frequency is equal to the FSB (CPU Host Frequency) multiplied by the multiplier (Multiplier),
Frequency = FSB × multiplier
In fact, the multiplier is not the frequency, just a multiple of the frequency multiplier is set in the CPU. The FSB is the frequency of the generator in the computer's motherboard is the computer's clock standard, also known as the system clock frequency. For example, a CPU multiplier ratio is 10, plus its FSB is 200 MHz, the CPU clock speed is equivalent to
200 MHz x 10 = 2000 MHz = 2.0 GHz
(2) front side bus concept
Front Side Bus (FSB) CPU with the motherboard's North Bridge (North Bridge) linked to the bus, it is the frequency that the CPU and the outside world (memory, AGP bus, PCI bus, etc.) the speed of data transmission. Before the advent of the Pentium 4, FSB frequency and FSB is the same. However, as computer technology continues to evolve, it is found that the front side bus frequency higher than the FSB Therefore, the front-side bus with FSB different. On the Intel platform, the front side bus frequency is four times that of the FSB; in the AMD platform, the front-side bus frequency of 2 times the FSB. Since the emergence of AMD K8, AMD has memory controller integrated in the CPU's internal links between the CPU and memory no longer through the FSB and North Bridge of the front-side bus no longer exists. However, the Intel platform, the front-side bus still exists.
Nevertheless, it is still often the front-side bus with FSB confused with, until now.
(3) a variety of memory frequency name Discrimination
Online, and even the motherboard manual to the CPU-Z, is called a variety of computers of various frequencies far from uniform, so probably comb:
Core frequency (Core Frequency): also known as the memory of the true frequency or limit frequency refers to the memory chips capable of withstanding the limits of frequency, if added to its frequency over this figure more (memory over OC), it will refuse to work. The most common reaction is "blue screen".
Clock frequency (Clock Frequency): refers to the actual operating frequency of the memory. The title of this frequency, for example, the frequency of memory, the operating frequency, operating frequency, bus frequency, DRAM frequency. In Hong Kong and Taiwan said it was too veins. Known as "speed" on many occasions also frequency.
The data frequency (Date Frequency), also known as the equivalent frequency or transmit frequency.
The three names in order not to cause confusion, memory frequency to retain only the core frequency, clock frequency and data frequency. However, some will not lead to misunderstanding, and appropriate to the occasion and the theme will clock frequency is called the operating frequency, operating frequency and bus frequency.
4 classes and attributes of the memory
For the average user, memory, three types: SDRAM memory, DDR SDRAM memory (also known as DDR or DDR1) and DDR2 SDRAM (referred to as DDR2). DDR3 memory soon after, not yet widely used.
SDRAM (synchronous dynamic random access memory), the DRAM Synchronous, said it was "synchronous dynamic random access memory" means that the speed of its work is synchronized with the system bus speed, which in one clock cycle only at the rising edge of the transmission
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times the data, this memory core frequency (Core frequency), the clock frequency (Clock freq.) and data frequency (Data freq.) is consistent.
DDR SDRAM stands for Double Data Rate SDRAM is the meaning of double data rate synchronous dynamic random access memory, DDR memory is evolved on the basis of SDRAM memory, it can be a data clock rise and fall of each transmission, therefore , its clock frequency and core frequency is equal, but its data frequency is doubled Fan of. That the core frequency, memory clock frequency and data frequency of three 1:1:2 relationship.
DDR2 DDR memory on the basis of the data off than DDR, use of special techniques that can be handled than doubled. That is, did the memory core frequency, clock frequency and data rate among the ratio 1:2:4.
The relationship between the frequency characteristics of the three kinds of memory and a few frequencies as follows:
Table 1 three memory frequency relationship
SDRAM, DDR1 and DDR2-400 already has been eliminated, however, in the old computer, the memory of the three specifications is still exist. For example, in 2002, I purchased IBM Black Edition, was considered more advanced, but its memory is SDRAM, capacity is only 128MB. Upgrading the speed of the computer is really fast.
5.Intel platform memory and CPU synchronization conditions
In order to ensure memory safety at work, add to the frequency of the memory can not be too high; in order to ensure the speed of your computer, plus the memory frequency should match with the CPU speed, not too low, therefore the memory requirements for synchronization (Synchronize), memory synchronization? There are various versions of the Internet, some said: "The memory frequency is equal to the FSB is the memory synchronization; Some said:" equal to the memory clock frequency and FSB is the memory synchronous. For example, when the FSB is 133 MHz, the motherboard supports SDRAM, it should be accompanied by PC133 memory; motherboard supports DDR1, together with a DDR 266 memory. These claims are of course correct.
However, for DDR2 memory, if I am: on the Intel platform, equal to the memory clock frequency and FSB is the memory synchronous "have a problem. For example, for the FSB = 800 MHz CPU, FSB equal to 200 MHz in this case, together with the DDR2-800 is the synchronization. This is not the memory clock frequency equal to the FSB ", but the memory clock frequency is equal to twice the FSB is the memory synchronous. So, I think, DDR2 memory is also included, it should be synchronized conditions to the memory core frequency is equal to the FSB synchronous memory "is accurate.
Of course, can also be separated from DDR2 with SDRAM, DDR, such as can say: "When the choice of DDR2 memory, FSB and memory clock frequency ratio of 1:2, that is, memory synchronization.
Example 1. Intel production of the CPU FSB is 200 MHz, if equipped with DDR memory, should be equipped with what type of memory is the memory synchronous?
A: For DDR memory, the core frequency is equal to the FSB memory synchronization, the core frequency is 200 MHz memory is DDR400, DDR400 memory should choose. Of course, said: "DDR memory, the clock frequency is equal to FSB memory synchronization when the FSB is 200MHz, DDR400 memory, we should choose."
Cases. Intel production of the CPU FSB is 200 MHz with DDR2 memory, should be equipped with what type of memory is the memory synchronous?
A: DDR2 memory, the core frequency is equal to the FSB memory synchronization, the core frequency is 200MHz, the memory is DDR2-800, should choose DDR800 memory. Of course, you can say: "DDR2 memory, FSB clock frequency ratio of 1:2 is the memory synchronous, therefore, when the FSB is 200 Mhz, select the DDR800 memory, because the DDR2-800 memory clock frequency is 400MHz with the FSB is a 1:2 relationship. "
The table below, listed in the different FSB conditions, how to select the memory. Single-frequency synchronization point of view, remove the table "dual DDR" in the "double" word is also a memory synchronization.
Table 2 memory reasonable matching table
Note: DDR memory slots with DDR2 memory slot is not the same, you should choose what memory to the motherboard.
6. The FSB bandwidth and memory bandwidth to match the conditions
When the select memory, in addition to the synchronization requirements of the memory, there is an important condition is the requirement of memory bandwidth and front-side bus (FSB) bandwidth equal to the best. If memory bandwidth is less than the bandwidth of the FSB, the CPU wait time will increase; if the memory bandwidth is greater than the FSB, the formation of a waste of memory resources.
For platforms that support DDR1, if the FSB is 200 MHz, single-memory synchronization point using a DDR400 can, however, because the FSB frequency is four times the FSB is 800 MHz, the bandwidth of 800 MHz x 64b ÷ 8b / B = 6.4 GB / s, the bandwidth of DDR400 is only 3.2 GB / s. Therefore, in order to match the memory bandwidth with the bandwidth of the FSB, it should be added to the same memory DDR400 up dual channel operation.
The platform supports DDR2, if the FSB is 200MHz, as long as with a DDR2-800, both to meet the memory synchronization requirements, but also meet the matching requirements of bandwidth.
The bandwidth of the matching conditions, can calculate the bandwidth method to determine, from the perspective of frequency, as long as the memory data frequency is equal to the frequency of the FSB is the bandwidth matches. For example, the data frequency of DDR2-800 dual channel DDR400 800 MHz FSB frequency of 800 MHz, so with the best mix.
In short, if added to the memory frequency is too high, the consequences of the "blue screen" or computer unstable; add to the memory frequency is too low, is a waste of resources of computer frequency. Bandwidth does not match the consequences of a waste of resources. Meets the memory synchronization, but also to meet the bandwidth matching, is the memory and the CPU with.
7. Intel platform memory asynchronous setting method
What is the memory asynchronously? In order to achieve some kind of memory work with the FSB frequency, referred to as memory asynchronous (Asynchronize),. The so-called memory and CPU with how to adapt to changes in CPU frequency is actually the memory frequency. For example, when the computer's CPU FSB from 166 MHz overclocked to 200 MHz, the added memory frequency will follow the upgrade to 200 MHz, so that memory can continue to work? The
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sole coated tip Yue Mei deceive play the occasion of the frightened rural the acyl Gu the carbuncle deceive Xian sodium Germany to decorated ? 66 MHz, unchanged, or only small changes. When the memory frequency is higher than the frequency of the CPU, is generally not subject to specialized settings, because the memory frequency are backward compatible. However, if you want to make this memory in the higher frequency operation, but also can be used for asynchronous memory settings so that the memory work at higher frequencies, to achieve the best use.
Memory asynchronously in the BIOS settings, current motherboard support most of the memory asynchronous technology. Of induction, set the following various, as described below:
⑴ directly regulates the maximum memory frequency increase or decrease - ± 33 MHz of the provisions of the early memory asynchronous technology is to use this solution. For example, when the P3 processor running at 100 MHz FSB through the BIOS settings, memory can be run asynchronously in the two frequencies of 133 MHz or 66 MHz.
⑵ the provisions of sub - which provides that the ratio of the FSB and memory clock frequency, frequency ratio and this ratio is called the divider coefficient (DRAM Frequency Ratio). Divider coefficient setting the value of a variety of different motherboards have different setting values, such as: 1:1 (synchronous), 1: 1.33, 4:3,4:5,5:4,12:13 . Divide factor greater than 1, the memory frequency is less than the FSB; divider coefficient is less than 1:00 is the memory frequency is greater than the FSB. For example, when the FSB is 200 MHz in the BIOS, you choose the sub-frequency coefficient is 5:4, then the memory frequency is 200 MHz x 4 ÷ 5 = 160 MHz, quite DDR320. If you install the memory is DDR333 or DDR2-667, exactly matching (memory frequency is slightly larger, do no harm).
⑶ set the memory multiplier (System Memory Multiplier) - Gigabyte (GIGABYTE) p31 motherboard is set. Multiplier in the BIOS options are: Auto (default actual installed memory on the motherboard), 3.33,3,4 +, 2.5 and 2. When the FSB is 200Mhz actual installed memory is DDR2-800, if you choose multiplier "3.33", then the memory clock frequency (Memory Frequency) will show "800 667", "800" you actually installed on the motherboard DDR2-800; "667" is to tell you: DDR2-667 asynchronous to mean, that is actually running in memory clock frequency is 333 MHz instead of 400 MHz.
⑷ directly - for example, the memory clock frequency (DRAM Frequency) Asustek (ASUS), P5E-VM motherboard BIOS setup options are: Auto, DDR2-667, DDR2-800, DDR2-834, DDR2-888 memory model DDR2-1000 DDR2-1112 and DDR2 = 1333 8 option, you intend to asynchronous memory to what extent, directly corresponding to the model chosen can be simple and straightforward. However, you can only choose within this range.
Example 3. FSB to 200 MHz front side bus frequency is 800 MHz Intel platform motherboard is installed on the DDR2-800 memory, when the FSB overclocked to 250 MHz, memory clock frequency is the number? If you do not want to upgrade the existing memory, how to set the memory asynchronous?
A: From the given conditions, install the DDR2-800 memory to meet the memory synchronization conditions (FSB: Memory clock frequency = 1:2), DDR2-800 memory clock frequency is 400 MHz.
When the FSB to 250MHz, the memory clock frequency synchronization upgrade. The memory clock frequency of 250MHz x 2 = 500MHz, quite of DDR2-1000. Memory overclocking, should upgrade the memory to DDR2-1066 go. If you want to use DDR2-800 memory, and can do the memory asynchronous settings. Gigabyte p31 motherboard, for example as follows:
In the beginning of the boot, click the "Del" key to enter the BIOS → use the up and down arrow keys to select the "MB Intelligent Tweaker (frequency / voltage control)" → Enter and select the "System Memory Multiplier (SPD) memory multiplier adjustment "→ select" 3.33 ", then" Memory Frequency memory clock adjustment "appears" 800 667 "two sets of figures, one of the" 800 "is your actual installed memory DDR2-800;" 667 " is asynchronous memory frequency of DDR2-667, the clock frequency of 333 MHz, DDR2-800 memory can be competent, however, the speed of the corresponding down.
Instructions in the "memory" and "clock" is Hong Kong and Taiwan terms, respectively, the meaning of "memory" and "clock frequency".
8.AMD platform method of calculating the actual memory frequency
On the Intel platform, the memory controller (Memory Controller) is placed within the North Bridge (North Bridge), the memory associated with CPU Front Side Bus (FSB), therefore, we calculate the Intel platform memory frequency above FSB as reference. AMD CPUs (the K8 and beyond) platform, the memory controller is placed within the CPU, so the calculation of the memory frequency of the AMD platform, based on CPU clock speed as a reference. Moreover, in the AMD platform, the asynchronous method of calculating with the synchronization method of calculating any difference.
In the BIOS memory frequency (in the BIOS, the memory frequency commonly used in English DRAM Frequency, Memory Frequency, or the Memory the Clock Frequency) is set to "Auto" or "By SPD", the memory controller will automatically detect your type and parameters of the memory installed on the motherboard, as long as you install the memory the motherboard supports the memory controller for you automatically calculated in the actual operation on the memory frequency, you can wash its hands of it.
If you select the memory core frequency is equal to the CPU FSB (for example, when the FSB is 200Mhz, you use DDR400 or DDR2-800), and this method is set (ie, computer memory frequency is automatically set for you the actual installation. The memory frequency), in fact, is the AMD platform synchronization settings.
However, with the Intel platform, the AMD platform, even if this synchronization settings, and its operating frequency and the nominal value may also vary. For example, you clocked at 2.2GHz, the multiplier is DDR2-800 memory, the installation of the AMD platform 11, the memory operating frequency is not 400MHz, but 366MHz, which is quite DDR2-372 memory. Why is there such a situation, with the special calculation method for the AMD platform, the memory controller design, the following will be introduced.
On the AMD platform, do memory asynchronous set, rarely used the divider ratio that are direct memory model. For example: DDR400,
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DDR2-400, DDR2-533, DDR2-667, DDR2-800, DDR2-1066, DDR2-1333 and so on.
AMD platform, the memory of the actual work is how to calculate? About the steps are as follows:
⑴ set the memory frequency in BIOS: if you actually installed in the memory slots on the memory core frequency is equal to the FSB in the BIOS set the memory frequency to select "Auto" or "By SPD", which means that you do is the memory synchronization settings. However, because the AMD platform, the memory operating frequency is determined by the CPU frequency, so only the memory clock frequency can be divisible by the CPU frequency, memory operating frequency to its nominal frequency is consistent .
It should be clear: you set in the BIOS memory frequency, the same as the actual frequency of memory installed on the motherboard; or may not be the same. If the frequency you set in the BIOS is lower or higher than the frequency of memory actually installed in the memory slot, memory asynchronous set. However, the current DDR2 memory overclocked to allow the limited scope of the current motherboard is mostly higher than the motherboard memory frequency setting options.
⑵ calculate the frequency division factor: First calculate the memory controller automatically sets the frequency division multiple DIV (Divider), often referred to as the divider factor:
DIV = CPU nominal frequency ÷ memory clock settings in the BIOS
If DIV decimal, then it should carry an integer, for example, 7.4 into 8. This is to ensure the safety of memory. Identify unclear whether the binary calculated DIV after the decimal point the number is very small, should take on more of the decimal point of the divisor (eg, 133) a few (for example, take 133.33333), and then the calculator or computer to calculate the DIV, it is easy to discern whether it should be binary.
If the calculated DIV is less than 5, it will be taken as 5. This is an important rule. However, because today's high CPU frequency, so this rule is often ignored.
The calculated value of the DIV is fixed in the memory controller on the CPU inside is not going to change because of the changes in the motherboard.
⑶ calculate the actual memory clock frequency: know the memory frequency division multiple memory clock frequency using the following formula:
The actual memory clock frequency = ÷ memory of the actual frequency of the CPU frequency division multiple
In the calculation, note that the difference between "nominal frequency" and "actual frequency". If you do not overclock, the two are equal.
The calculation results came out, you can determine the memory you choose is appropriate.
Example 4: CPU AMD Athlon (Athlon) 64 3200 +, clocked at 2.0 GHz, FSB is 200 MHz, intended to adopt a DDR400 memory (Auto) setting in the BIOS to do this, ask: (1) sub- The frequency of multiples? ⑵ the actual frequency of the memory?
Solution: (1) because the CPU clock speed is equal to 2000 MHz; DDR400 clock frequency equal to 400MHz / 2 = 200 MHz, memory sub-frequency multiples = 2000 MHz, ÷ 200 MHz = 10;
⑵ in question did not say that overclocking the memory clock frequency = 2000 MHz, ÷ 10 = 200 MHz, the memory is 200 MHz, therefore, to install DDR400 memory is the memory synchronous state.
Example 5. CPU Sempron 3200 +, clocked at 1.8 GHz, motherboard FSB is 200 MHz, the selection of DDR II 800 memory, and asked: (1) divided by a multiple of the number of how many? ⑵ memory clock frequency?
Solution: (1) sub-frequency coefficient DIV = 1800 MHz ÷ 400 MHz = 4.5, should be taken to be 5;
⑵ because the title did not say that overclocking the memory clock frequency = 1800 MHz, ÷ 5 = 360 MHz,. Upcoming memory relegated to DDR2-720. Because of the frequency of the memory is backward-compatible, so, such a configuration is also possible, but also that memory to run in synchronization status.
Example 6. A AMD CPU Nominal frequency is 2.0 GHz, FSB 200 MHz, set the BIOS memory is DDR2-800. FSB super to 250 MHz, and how to select the memory?
Solution: (1) sub-frequency multiples DIV = 2000 MHz ÷ 800 MHz, ÷ 2 = 5.0;
(2) When the FSB to 250MHz, the actual frequency is 250MHz x 10 = 2500 MHz, memory clock frequency = 2500 MHz, ÷ 5 = 500 MHz, this frequency is the clock frequency, it is multiplied by 2 memory The data frequency corresponding to the DDR2-1000. Therefore, in this case, DDR2-800 is overclocking, may make your computer run unstable, and should be replaced as DDR2-1000 memory to do.
If you do not want to replace the now installed on the motherboard, DDR2-800 memory, you can also do the memory asynchronous settings. The BIOS memory frequency is set a little lower, for example, set to DDR2-667, In this way, the DIV = 2000MHz ÷ 333MHz = 6. Overclocked frequency is 250MHz x 10 = 2500 MHz, 2500 MHz, ÷ 6 = 416 MHz memory clock frequency will be, if you now install the DDR2-800 memory physical good, such a small frequency of "overload" , should be can afford, she says.
If you do not worry, the memory frequency in the BIOS setting and then a little lower, for example set to DDR2-533, this time the DIV = 2000MHz ÷ 266MHz = 7.5, should carry is taken as 8. In this way, the clock speed of the CPU overclocked to 2500 MHz, memory clock frequency is 2500 MHz ÷ 8 = as 312.5MHz, quite of DDR2-625, so that you installed on the motherboard, DDR2-800 memory work lightly and more. However, this is in exchange for the sacrifice of memory speed.
The following table is a table calculated in accordance with the above reasoning, it is to explain the relationship between the BIOS set the memory frequency (DRAM the Frequency or Memory Frequency) with the actual memory frequency. Table "divide" we said above, divided by a multiple of the DIV; actual operating frequency of the memory clock frequency, the premise is not overclocked. Table using the The Scarlet Letter, said the sub-frequency and the number of clock frequency, and that calculated from the DIV less than 5, the memory controller into 5.
When overclocking the answer to the above three examples can be directly from the table to check out. However, the overclocking situation in the table divided by the coefficient ("divide") is still available, simply divide it by overclocking frequency to get the memory working frequency. This method has been used in Example 3.
Table 3 in the AMD platform BIOS settings the effect of frequency table
Note: from the table
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seen: clock frequency settings in the BIOS can be evenly divisible by the frequency of the frequency of memory can be to make full use of the frequency (Table in blue bold figures) Otherwise, the memory The frequency will be reduced. This is the setting of the memory controller in order to protect the memory overclocking sake.
Example 8. Frequency in the AMD platform is a 1.6GHz processor multiplier is 8, when the memory frequency is set in the BIOS DDR 333 memory operating frequency is?
A: The DIV = 1600 MHz/166.66 = 9.6, is taken as 10, the memory operating frequency is 1600 MHz ÷ 10 = 160 MHz, quite DDR320. This example: If the memory clock frequency is not divisible by the frequency of the CPU, memory can not be fully synchronized with the CPU.
9 With regard to dual-channel memory technology
Manufacturing CPU technology has improved continuously, the CPU frequency to enhance fast, but the level of technology of manufacturing the memory can not simultaneously improve the speed of the memory is always behind the CPU. For example, in a few years ago, the FSB frequency to 800 MHz and memory frequency has been unable to break through DDR400. Memory synchronization point of view, DDR400 memory with FSB 800 MHz CPU is synchronized. However, from the perspective of bandwidth matching, is not matched. So there was a dual-channel memory technology.
What is dual channel? The dual-channel system includes two independent, complementary smart memory controller, in theory, the two memory controllers are able to simultaneously between zero delay operation. The structural principle of the following figure shown on the right.
Dual channel with memory, when the controller B ready for the next access memory, the controller A read / write main memory, and vice versa. This complementary function of both the memory controller can make the wait time reduced by 50%. Two dual-channel DDR memory controller functionality is exactly the same. Ordinary single-channel memory system with a 64-bit memory controller, dual-channel memory system, there are two 64-bit memory controller, with a 128bit memory in dual channel mode bits wide, so in theory, the memory bandwidth doubled. For example, the single-channel DDR400 bandwidth is 3.2GB / s, if the same memory plus a dual-channel bandwidth into a 6.4GB / s.
Therefore, for the front-side bus is 800 MHz platform with two DDR 400 memory, dual channel, not only to meet the frequency synchronization requirements, but also to meet the matching requirements of bandwidth. However, for DDR2 memory, just with a DDR2-800 memory on it. In doing so, also can satisfy the synchronization requirements, but also to meet the bandwidth requirements. If you want to dual-channel, only to add a DDR2-800 memory. If you want to save a little, when you intend to use two DDR2-400 memory settings for dual channel to cope with 800 MHz FSB, while the bandwidth can meet the requirements, but the FSB is 200MHz, memory clock frequency is 200 MHz, can not meet the installation DDR2 memory FSB and memory clock frequency ratio of 1:2 requirement, therefore, the memory is out of sync, unless you do the memory asynchronous set, otherwise, make the computer unable to stabilize the operation.
However, we often see this argument: "dual-channel with two DDR2-533 memory can be used on the FSB is 1066 MHz platform" sort of argument. I say this is wrong, because each channel are independent, when you set the dual channel can indeed increase the bandwidth, however, the memory clock frequency is not doubled. The following experimental results can be seen: the single-channel, the clock frequency of the memory (DRAM Frequency) 400 MHz, then one is DDR2-800 memory, dual-channel detection, the clock frequency of 400 MHz, and set up a dual-channel double.
By the test results can be seen, the dual-channel memory capacity of 1024 MB expanded to 2048 MB. And indicates that the dual-channel (OC mode) is symmetrical, This means that the bandwidth is doubled Fan of.
Note: "FSB: memory test results" may wish to "FSB: Memory clock frequency," Therefore, the ratio of 1:2, or 200 Mhz: 400 MHz, Does CPU-Z FSB and FSB confuse? !
Older motherboard for dual channel memory requirements more demanding, we must first motherboard chip support, was also requested from the same manufacturer specifications, the same memory capacity installed in the correct way in order to form a dual-channel. However, the current motherboard mostly supports dual channel, and the use of the FMT technology has been greatly reduced, dual-channel memory specifications and capacity requirements, so dual channel is a relatively easy thing to do. However, for more than three memory slots motherboard, if your memory is not exactly the same, the installation must be installed in accordance with the motherboard manual. The principle is the same size of memory of "separated by interpolation or interpolation method for a group of two slots of the same color. Have to look at the motherboard manual to insert before, because there is no uniform standard in this regard, therefore, must be manual shall prevail. .
Check whether dual-channel, you can use special software to check. Such as CPU-Z makes EVEREST, SiSofyware, Sandra and so on.
but is often confused with, mix; with a frequency of various names, various names are often mixed; four Intel CPU and AMD CPU features, mix them with the memory is not the same, but is often confused with; five before AMD K8 CPU K8 and CPU features, is often confused with; memory settings for the various motherboard manufacturers often use different methods and name, easy to make people confused; seven is the age of article writing is not specified, do not know which age, what type of memory; (8) is to write the author's level uneven, cohabitation is sometimes difficult to distinguish right and wrong . Therefore, in the study of memory, knowledge, and I really spend a lot of time. See much more, want more, of course, also the initiation of some personal opinion. In order to consolidate the results of my study, I have made this summary memo. Of course, want to give the same "rookie" netizens by reference, and we welcome the "heroes" were corrected.
The concept of CPU frequency
CPU frequency is the speed of your computer, we often say is very important. However, the CPU itself is just a chip, does not produce frequency, frequency computer motherboard plus to it. Its frequency is the frequency that it is functional, if the frequency is too high, that is it for the use of excessive overclocking, it will "strike" or even burned. CPU frequency is equal to the FSB (CPU Host Frequency) multiplied by the multiplier (Multiplier),
Frequency = FSB × multiplier
In fact, the multiplier is not the frequency, just a multiple of the frequency multiplier is set in the CPU. The FSB is the frequency of the generator in the computer's motherboard is the computer's clock standard, also known as the system clock frequency. For example, a CPU multiplier ratio is 10, plus its FSB is 200 MHz, the CPU clock speed is equivalent to
200 MHz x 10 = 2000 MHz = 2.0 GHz
(2) front side bus concept
Front Side Bus (FSB) CPU with the motherboard's North Bridge (North Bridge) linked to the bus, it is the frequency that the CPU and the outside world (memory, AGP bus, PCI bus, etc.) the speed of data transmission. Before the advent of the Pentium 4, FSB frequency and FSB is the same. However, as computer technology continues to evolve, it is found that the front side bus frequency higher than the FSB Therefore, the front-side bus with FSB different. On the Intel platform, the front side bus frequency is four times that of the FSB; in the AMD platform, the front-side bus frequency of 2 times the FSB. Since the emergence of AMD K8, AMD has memory controller integrated in the CPU's internal links between the CPU and memory no longer through the FSB and North Bridge of the front-side bus no longer exists. However, the Intel platform, the front-side bus still exists.
Nevertheless, it is still often the front-side bus with FSB confused with, until now.
(3) a variety of memory frequency name Discrimination
Online, and even the motherboard manual to the CPU-Z, is called a variety of computers of various frequencies far from uniform, so probably comb:
Core frequency (Core Frequency): also known as the memory of the true frequency or limit frequency refers to the memory chips capable of withstanding the limits of frequency, if added to its frequency over this figure more (memory over OC), it will refuse to work. The most common reaction is "blue screen".
Clock frequency (Clock Frequency): refers to the actual operating frequency of the memory. The title of this frequency, for example, the frequency of memory, the operating frequency, operating frequency, bus frequency, DRAM frequency. In Hong Kong and Taiwan said it was too veins. Known as "speed" on many occasions also frequency.
The data frequency (Date Frequency), also known as the equivalent frequency or transmit frequency.
The three names in order not to cause confusion, memory frequency to retain only the core frequency, clock frequency and data frequency. However, some will not lead to misunderstanding, and appropriate to the occasion and the theme will clock frequency is called the operating frequency, operating frequency and bus frequency.
4 classes and attributes of the memory
For the average user, memory, three types: SDRAM memory, DDR SDRAM memory (also known as DDR or DDR1) and DDR2 SDRAM (referred to as DDR2). DDR3 memory soon after, not yet widely used.
SDRAM (synchronous dynamic random access memory), the DRAM Synchronous, said it was "synchronous dynamic random access memory" means that the speed of its work is synchronized with the system bus speed, which in one clock cycle only at the rising edge of the transmission
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times the data, this memory core frequency (Core frequency), the clock frequency (Clock freq.) and data frequency (Data freq.) is consistent.
DDR SDRAM stands for Double Data Rate SDRAM is the meaning of double data rate synchronous dynamic random access memory, DDR memory is evolved on the basis of SDRAM memory, it can be a data clock rise and fall of each transmission, therefore , its clock frequency and core frequency is equal, but its data frequency is doubled Fan of. That the core frequency, memory clock frequency and data frequency of three 1:1:2 relationship.
DDR2 DDR memory on the basis of the data off than DDR, use of special techniques that can be handled than doubled. That is, did the memory core frequency, clock frequency and data rate among the ratio 1:2:4.
The relationship between the frequency characteristics of the three kinds of memory and a few frequencies as follows:
Table 1 three memory frequency relationship
SDRAM, DDR1 and DDR2-400 already has been eliminated, however, in the old computer, the memory of the three specifications is still exist. For example, in 2002, I purchased IBM Black Edition, was considered more advanced, but its memory is SDRAM, capacity is only 128MB. Upgrading the speed of the computer is really fast.
5.Intel platform memory and CPU synchronization conditions
In order to ensure memory safety at work, add to the frequency of the memory can not be too high; in order to ensure the speed of your computer, plus the memory frequency should match with the CPU speed, not too low, therefore the memory requirements for synchronization (Synchronize), memory synchronization? There are various versions of the Internet, some said: "The memory frequency is equal to the FSB is the memory synchronization; Some said:" equal to the memory clock frequency and FSB is the memory synchronous. For example, when the FSB is 133 MHz, the motherboard supports SDRAM, it should be accompanied by PC133 memory; motherboard supports DDR1, together with a DDR 266 memory. These claims are of course correct.
However, for DDR2 memory, if I am: on the Intel platform, equal to the memory clock frequency and FSB is the memory synchronous "have a problem. For example, for the FSB = 800 MHz CPU, FSB equal to 200 MHz in this case, together with the DDR2-800 is the synchronization. This is not the memory clock frequency equal to the FSB ", but the memory clock frequency is equal to twice the FSB is the memory synchronous. So, I think, DDR2 memory is also included, it should be synchronized conditions to the memory core frequency is equal to the FSB synchronous memory "is accurate.
Of course, can also be separated from DDR2 with SDRAM, DDR, such as can say: "When the choice of DDR2 memory, FSB and memory clock frequency ratio of 1:2, that is, memory synchronization.
Example 1. Intel production of the CPU FSB is 200 MHz, if equipped with DDR memory, should be equipped with what type of memory is the memory synchronous?
A: For DDR memory, the core frequency is equal to the FSB memory synchronization, the core frequency is 200 MHz memory is DDR400, DDR400 memory should choose. Of course, said: "DDR memory, the clock frequency is equal to FSB memory synchronization when the FSB is 200MHz, DDR400 memory, we should choose."
Cases. Intel production of the CPU FSB is 200 MHz with DDR2 memory, should be equipped with what type of memory is the memory synchronous?
A: DDR2 memory, the core frequency is equal to the FSB memory synchronization, the core frequency is 200MHz, the memory is DDR2-800, should choose DDR800 memory. Of course, you can say: "DDR2 memory, FSB clock frequency ratio of 1:2 is the memory synchronous, therefore, when the FSB is 200 Mhz, select the DDR800 memory, because the DDR2-800 memory clock frequency is 400MHz with the FSB is a 1:2 relationship. "
The table below, listed in the different FSB conditions, how to select the memory. Single-frequency synchronization point of view, remove the table "dual DDR" in the "double" word is also a memory synchronization.
Table 2 memory reasonable matching table
Note: DDR memory slots with DDR2 memory slot is not the same, you should choose what memory to the motherboard.
6. The FSB bandwidth and memory bandwidth to match the conditions
When the select memory, in addition to the synchronization requirements of the memory, there is an important condition is the requirement of memory bandwidth and front-side bus (FSB) bandwidth equal to the best. If memory bandwidth is less than the bandwidth of the FSB, the CPU wait time will increase; if the memory bandwidth is greater than the FSB, the formation of a waste of memory resources.
For platforms that support DDR1, if the FSB is 200 MHz, single-memory synchronization point using a DDR400 can, however, because the FSB frequency is four times the FSB is 800 MHz, the bandwidth of 800 MHz x 64b ÷ 8b / B = 6.4 GB / s, the bandwidth of DDR400 is only 3.2 GB / s. Therefore, in order to match the memory bandwidth with the bandwidth of the FSB, it should be added to the same memory DDR400 up dual channel operation.
The platform supports DDR2, if the FSB is 200MHz, as long as with a DDR2-800, both to meet the memory synchronization requirements, but also meet the matching requirements of bandwidth.
The bandwidth of the matching conditions, can calculate the bandwidth method to determine, from the perspective of frequency, as long as the memory data frequency is equal to the frequency of the FSB is the bandwidth matches. For example, the data frequency of DDR2-800 dual channel DDR400 800 MHz FSB frequency of 800 MHz, so with the best mix.
In short, if added to the memory frequency is too high, the consequences of the "blue screen" or computer unstable; add to the memory frequency is too low, is a waste of resources of computer frequency. Bandwidth does not match the consequences of a waste of resources. Meets the memory synchronization, but also to meet the bandwidth matching, is the memory and the CPU with.
7. Intel platform memory asynchronous setting method
What is the memory asynchronously? In order to achieve some kind of memory work with the FSB frequency, referred to as memory asynchronous (Asynchronize),. The so-called memory and CPU with how to adapt to changes in CPU frequency is actually the memory frequency. For example, when the computer's CPU FSB from 166 MHz overclocked to 200 MHz, the added memory frequency will follow the upgrade to 200 MHz, so that memory can continue to work? The
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sole coated tip Yue Mei deceive play the occasion of the frightened rural the acyl Gu the carbuncle deceive Xian sodium Germany to decorated ? 66 MHz, unchanged, or only small changes. When the memory frequency is higher than the frequency of the CPU, is generally not subject to specialized settings, because the memory frequency are backward compatible. However, if you want to make this memory in the higher frequency operation, but also can be used for asynchronous memory settings so that the memory work at higher frequencies, to achieve the best use.
Memory asynchronously in the BIOS settings, current motherboard support most of the memory asynchronous technology. Of induction, set the following various, as described below:
⑴ directly regulates the maximum memory frequency increase or decrease - ± 33 MHz of the provisions of the early memory asynchronous technology is to use this solution. For example, when the P3 processor running at 100 MHz FSB through the BIOS settings, memory can be run asynchronously in the two frequencies of 133 MHz or 66 MHz.
⑵ the provisions of sub - which provides that the ratio of the FSB and memory clock frequency, frequency ratio and this ratio is called the divider coefficient (DRAM Frequency Ratio). Divider coefficient setting the value of a variety of different motherboards have different setting values, such as: 1:1 (synchronous), 1: 1.33, 4:3,4:5,5:4,12:13 . Divide factor greater than 1, the memory frequency is less than the FSB; divider coefficient is less than 1:00 is the memory frequency is greater than the FSB. For example, when the FSB is 200 MHz in the BIOS, you choose the sub-frequency coefficient is 5:4, then the memory frequency is 200 MHz x 4 ÷ 5 = 160 MHz, quite DDR320. If you install the memory is DDR333 or DDR2-667, exactly matching (memory frequency is slightly larger, do no harm).
⑶ set the memory multiplier (System Memory Multiplier) - Gigabyte (GIGABYTE) p31 motherboard is set. Multiplier in the BIOS options are: Auto (default actual installed memory on the motherboard), 3.33,3,4 +, 2.5 and 2. When the FSB is 200Mhz actual installed memory is DDR2-800, if you choose multiplier "3.33", then the memory clock frequency (Memory Frequency) will show "800 667", "800" you actually installed on the motherboard DDR2-800; "667" is to tell you: DDR2-667 asynchronous to mean, that is actually running in memory clock frequency is 333 MHz instead of 400 MHz.
⑷ directly - for example, the memory clock frequency (DRAM Frequency) Asustek (ASUS), P5E-VM motherboard BIOS setup options are: Auto, DDR2-667, DDR2-800, DDR2-834, DDR2-888 memory model DDR2-1000 DDR2-1112 and DDR2 = 1333 8 option, you intend to asynchronous memory to what extent, directly corresponding to the model chosen can be simple and straightforward. However, you can only choose within this range.
Example 3. FSB to 200 MHz front side bus frequency is 800 MHz Intel platform motherboard is installed on the DDR2-800 memory, when the FSB overclocked to 250 MHz, memory clock frequency is the number? If you do not want to upgrade the existing memory, how to set the memory asynchronous?
A: From the given conditions, install the DDR2-800 memory to meet the memory synchronization conditions (FSB: Memory clock frequency = 1:2), DDR2-800 memory clock frequency is 400 MHz.
When the FSB to 250MHz, the memory clock frequency synchronization upgrade. The memory clock frequency of 250MHz x 2 = 500MHz, quite of DDR2-1000. Memory overclocking, should upgrade the memory to DDR2-1066 go. If you want to use DDR2-800 memory, and can do the memory asynchronous settings. Gigabyte p31 motherboard, for example as follows:
In the beginning of the boot, click the "Del" key to enter the BIOS → use the up and down arrow keys to select the "MB Intelligent Tweaker (frequency / voltage control)" → Enter and select the "System Memory Multiplier (SPD) memory multiplier adjustment "→ select" 3.33 ", then" Memory Frequency memory clock adjustment "appears" 800 667 "two sets of figures, one of the" 800 "is your actual installed memory DDR2-800;" 667 " is asynchronous memory frequency of DDR2-667, the clock frequency of 333 MHz, DDR2-800 memory can be competent, however, the speed of the corresponding down.
Instructions in the "memory" and "clock" is Hong Kong and Taiwan terms, respectively, the meaning of "memory" and "clock frequency".
8.AMD platform method of calculating the actual memory frequency
On the Intel platform, the memory controller (Memory Controller) is placed within the North Bridge (North Bridge), the memory associated with CPU Front Side Bus (FSB), therefore, we calculate the Intel platform memory frequency above FSB as reference. AMD CPUs (the K8 and beyond) platform, the memory controller is placed within the CPU, so the calculation of the memory frequency of the AMD platform, based on CPU clock speed as a reference. Moreover, in the AMD platform, the asynchronous method of calculating with the synchronization method of calculating any difference.
In the BIOS memory frequency (in the BIOS, the memory frequency commonly used in English DRAM Frequency, Memory Frequency, or the Memory the Clock Frequency) is set to "Auto" or "By SPD", the memory controller will automatically detect your type and parameters of the memory installed on the motherboard, as long as you install the memory the motherboard supports the memory controller for you automatically calculated in the actual operation on the memory frequency, you can wash its hands of it.
If you select the memory core frequency is equal to the CPU FSB (for example, when the FSB is 200Mhz, you use DDR400 or DDR2-800), and this method is set (ie, computer memory frequency is automatically set for you the actual installation. The memory frequency), in fact, is the AMD platform synchronization settings.
However, with the Intel platform, the AMD platform, even if this synchronization settings, and its operating frequency and the nominal value may also vary. For example, you clocked at 2.2GHz, the multiplier is DDR2-800 memory, the installation of the AMD platform 11, the memory operating frequency is not 400MHz, but 366MHz, which is quite DDR2-372 memory. Why is there such a situation, with the special calculation method for the AMD platform, the memory controller design, the following will be introduced.
On the AMD platform, do memory asynchronous set, rarely used the divider ratio that are direct memory model. For example: DDR400,
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DDR2-400, DDR2-533, DDR2-667, DDR2-800, DDR2-1066, DDR2-1333 and so on.
AMD platform, the memory of the actual work is how to calculate? About the steps are as follows:
⑴ set the memory frequency in BIOS: if you actually installed in the memory slots on the memory core frequency is equal to the FSB in the BIOS set the memory frequency to select "Auto" or "By SPD", which means that you do is the memory synchronization settings. However, because the AMD platform, the memory operating frequency is determined by the CPU frequency, so only the memory clock frequency can be divisible by the CPU frequency, memory operating frequency to its nominal frequency is consistent .
It should be clear: you set in the BIOS memory frequency, the same as the actual frequency of memory installed on the motherboard; or may not be the same. If the frequency you set in the BIOS is lower or higher than the frequency of memory actually installed in the memory slot, memory asynchronous set. However, the current DDR2 memory overclocked to allow the limited scope of the current motherboard is mostly higher than the motherboard memory frequency setting options.
⑵ calculate the frequency division factor: First calculate the memory controller automatically sets the frequency division multiple DIV (Divider), often referred to as the divider factor:
DIV = CPU nominal frequency ÷ memory clock settings in the BIOS
If DIV decimal, then it should carry an integer, for example, 7.4 into 8. This is to ensure the safety of memory. Identify unclear whether the binary calculated DIV after the decimal point the number is very small, should take on more of the decimal point of the divisor (eg, 133) a few (for example, take 133.33333), and then the calculator or computer to calculate the DIV, it is easy to discern whether it should be binary.
If the calculated DIV is less than 5, it will be taken as 5. This is an important rule. However, because today's high CPU frequency, so this rule is often ignored.
The calculated value of the DIV is fixed in the memory controller on the CPU inside is not going to change because of the changes in the motherboard.
⑶ calculate the actual memory clock frequency: know the memory frequency division multiple memory clock frequency using the following formula:
The actual memory clock frequency = ÷ memory of the actual frequency of the CPU frequency division multiple
In the calculation, note that the difference between "nominal frequency" and "actual frequency". If you do not overclock, the two are equal.
The calculation results came out, you can determine the memory you choose is appropriate.
Example 4: CPU AMD Athlon (Athlon) 64 3200 +, clocked at 2.0 GHz, FSB is 200 MHz, intended to adopt a DDR400 memory (Auto) setting in the BIOS to do this, ask: (1) sub- The frequency of multiples? ⑵ the actual frequency of the memory?
Solution: (1) because the CPU clock speed is equal to 2000 MHz; DDR400 clock frequency equal to 400MHz / 2 = 200 MHz, memory sub-frequency multiples = 2000 MHz, ÷ 200 MHz = 10;
⑵ in question did not say that overclocking the memory clock frequency = 2000 MHz, ÷ 10 = 200 MHz, the memory is 200 MHz, therefore, to install DDR400 memory is the memory synchronous state.
Example 5. CPU Sempron 3200 +, clocked at 1.8 GHz, motherboard FSB is 200 MHz, the selection of DDR II 800 memory, and asked: (1) divided by a multiple of the number of how many? ⑵ memory clock frequency?
Solution: (1) sub-frequency coefficient DIV = 1800 MHz ÷ 400 MHz = 4.5, should be taken to be 5;
⑵ because the title did not say that overclocking the memory clock frequency = 1800 MHz, ÷ 5 = 360 MHz,. Upcoming memory relegated to DDR2-720. Because of the frequency of the memory is backward-compatible, so, such a configuration is also possible, but also that memory to run in synchronization status.
Example 6. A AMD CPU Nominal frequency is 2.0 GHz, FSB 200 MHz, set the BIOS memory is DDR2-800. FSB super to 250 MHz, and how to select the memory?
Solution: (1) sub-frequency multiples DIV = 2000 MHz ÷ 800 MHz, ÷ 2 = 5.0;
(2) When the FSB to 250MHz, the actual frequency is 250MHz x 10 = 2500 MHz, memory clock frequency = 2500 MHz, ÷ 5 = 500 MHz, this frequency is the clock frequency, it is multiplied by 2 memory The data frequency corresponding to the DDR2-1000. Therefore, in this case, DDR2-800 is overclocking, may make your computer run unstable, and should be replaced as DDR2-1000 memory to do.
If you do not want to replace the now installed on the motherboard, DDR2-800 memory, you can also do the memory asynchronous settings. The BIOS memory frequency is set a little lower, for example, set to DDR2-667, In this way, the DIV = 2000MHz ÷ 333MHz = 6. Overclocked frequency is 250MHz x 10 = 2500 MHz, 2500 MHz, ÷ 6 = 416 MHz memory clock frequency will be, if you now install the DDR2-800 memory physical good, such a small frequency of "overload" , should be can afford, she says.
If you do not worry, the memory frequency in the BIOS setting and then a little lower, for example set to DDR2-533, this time the DIV = 2000MHz ÷ 266MHz = 7.5, should carry is taken as 8. In this way, the clock speed of the CPU overclocked to 2500 MHz, memory clock frequency is 2500 MHz ÷ 8 = as 312.5MHz, quite of DDR2-625, so that you installed on the motherboard, DDR2-800 memory work lightly and more. However, this is in exchange for the sacrifice of memory speed.
The following table is a table calculated in accordance with the above reasoning, it is to explain the relationship between the BIOS set the memory frequency (DRAM the Frequency or Memory Frequency) with the actual memory frequency. Table "divide" we said above, divided by a multiple of the DIV; actual operating frequency of the memory clock frequency, the premise is not overclocked. Table using the The Scarlet Letter, said the sub-frequency and the number of clock frequency, and that calculated from the DIV less than 5, the memory controller into 5.
When overclocking the answer to the above three examples can be directly from the table to check out. However, the overclocking situation in the table divided by the coefficient ("divide") is still available, simply divide it by overclocking frequency to get the memory working frequency. This method has been used in Example 3.
Table 3 in the AMD platform BIOS settings the effect of frequency table
Note: from the table
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seen: clock frequency settings in the BIOS can be evenly divisible by the frequency of the frequency of memory can be to make full use of the frequency (Table in blue bold figures) Otherwise, the memory The frequency will be reduced. This is the setting of the memory controller in order to protect the memory overclocking sake.
Example 8. Frequency in the AMD platform is a 1.6GHz processor multiplier is 8, when the memory frequency is set in the BIOS DDR 333 memory operating frequency is?
A: The DIV = 1600 MHz/166.66 = 9.6, is taken as 10, the memory operating frequency is 1600 MHz ÷ 10 = 160 MHz, quite DDR320. This example: If the memory clock frequency is not divisible by the frequency of the CPU, memory can not be fully synchronized with the CPU.
9 With regard to dual-channel memory technology
Manufacturing CPU technology has improved continuously, the CPU frequency to enhance fast, but the level of technology of manufacturing the memory can not simultaneously improve the speed of the memory is always behind the CPU. For example, in a few years ago, the FSB frequency to 800 MHz and memory frequency has been unable to break through DDR400. Memory synchronization point of view, DDR400 memory with FSB 800 MHz CPU is synchronized. However, from the perspective of bandwidth matching, is not matched. So there was a dual-channel memory technology.
What is dual channel? The dual-channel system includes two independent, complementary smart memory controller, in theory, the two memory controllers are able to simultaneously between zero delay operation. The structural principle of the following figure shown on the right.
Dual channel with memory, when the controller B ready for the next access memory, the controller A read / write main memory, and vice versa. This complementary function of both the memory controller can make the wait time reduced by 50%. Two dual-channel DDR memory controller functionality is exactly the same. Ordinary single-channel memory system with a 64-bit memory controller, dual-channel memory system, there are two 64-bit memory controller, with a 128bit memory in dual channel mode bits wide, so in theory, the memory bandwidth doubled. For example, the single-channel DDR400 bandwidth is 3.2GB / s, if the same memory plus a dual-channel bandwidth into a 6.4GB / s.
Therefore, for the front-side bus is 800 MHz platform with two DDR 400 memory, dual channel, not only to meet the frequency synchronization requirements, but also to meet the matching requirements of bandwidth. However, for DDR2 memory, just with a DDR2-800 memory on it. In doing so, also can satisfy the synchronization requirements, but also to meet the bandwidth requirements. If you want to dual-channel, only to add a DDR2-800 memory. If you want to save a little, when you intend to use two DDR2-400 memory settings for dual channel to cope with 800 MHz FSB, while the bandwidth can meet the requirements, but the FSB is 200MHz, memory clock frequency is 200 MHz, can not meet the installation DDR2 memory FSB and memory clock frequency ratio of 1:2 requirement, therefore, the memory is out of sync, unless you do the memory asynchronous set, otherwise, make the computer unable to stabilize the operation.
However, we often see this argument: "dual-channel with two DDR2-533 memory can be used on the FSB is 1066 MHz platform" sort of argument. I say this is wrong, because each channel are independent, when you set the dual channel can indeed increase the bandwidth, however, the memory clock frequency is not doubled. The following experimental results can be seen: the single-channel, the clock frequency of the memory (DRAM Frequency) 400 MHz, then one is DDR2-800 memory, dual-channel detection, the clock frequency of 400 MHz, and set up a dual-channel double.
By the test results can be seen, the dual-channel memory capacity of 1024 MB expanded to 2048 MB. And indicates that the dual-channel (OC mode) is symmetrical, This means that the bandwidth is doubled Fan of.
Note: "FSB: memory test results" may wish to "FSB: Memory clock frequency," Therefore, the ratio of 1:2, or 200 Mhz: 400 MHz, Does CPU-Z FSB and FSB confuse? !
Older motherboard for dual channel memory requirements more demanding, we must first motherboard chip support, was also requested from the same manufacturer specifications, the same memory capacity installed in the correct way in order to form a dual-channel. However, the current motherboard mostly supports dual channel, and the use of the FMT technology has been greatly reduced, dual-channel memory specifications and capacity requirements, so dual channel is a relatively easy thing to do. However, for more than three memory slots motherboard, if your memory is not exactly the same, the installation must be installed in accordance with the motherboard manual. The principle is the same size of memory of "separated by interpolation or interpolation method for a group of two slots of the same color. Have to look at the motherboard manual to insert before, because there is no uniform standard in this regard, therefore, must be manual shall prevail. .
Check whether dual-channel, you can use special software to check. Such as CPU-Z makes EVEREST, SiSofyware, Sandra and so on.
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