Pay attention to the matching between CPU bandwidth and memory bandwidth! Don't let the memory slow down the CPU.

Http://bbs.xiyuit.com/thread-4143-1-1.htmlplease stay tuned for matching the CPU bandwidth and memory bandwidth! Don't let the memory slow down the CPU. Intel's CPU has certain requirements on memory bandwidth since P4. Why did Intel have to push Rambus to match P4? This is because both SDRAM and ddr ram are insufficient to meet P4's needs.

For details, FSB is P4 of 533 (external frequency: 133), and the data bandwidth requirement is 4.3 Gb/s (Yes
In this rough estimation, the bandwidth requirement for fsb800 p4 is 6.4 Gb/s with the CPU bandwidth = FSB × 8.
In the same period, DDR 400 only provides 3.2 Gb/s bandwidth (ddr400 is also called pc3200 memory, which is named after bandwidth). ddr266 bandwidth is 2.1 Gb/s, ddr333 has a bandwidth of 2.7 Gb/s. It can be seen that a single DDR memory cannot meet the requirements of fsb800 P4. When the CPU needs data, the memory cannot pass enough data, causing the CPU to be idle.

So intel worked hard to promote Rambus to match its own P4. However, Rambus costs and production capacity are everywhere, which is just as high as possible. Intel has to discard the 850 chipset and re-launch the 845 chipset that supports SDRAM to match P4. This may be the case when we buy P4 earlier. Motherboard In fact, the performance of P4 is restricted by the memory. The 845d, 848, and other chipsets that later support DDR single-channel memory did not solve the problem perfectly.

Later, the 865 chipset that supports "dual-channel" was used to solve the problem. The dual-channel ddr266 bandwidth meets the P4 of fsb533, while the dual-channel ddr400 meets the P4 of fsb800. This rule can be simply calculated as the memory nominal value * 2 = FSB frequency (Supplement: the actual memory operating frequency is half of the nominal value, that is, the memory of the nominal ddr400, the actual memory operating frequency is 200 MHz, DDR2 800 memory, and the actual operating frequency is 400 MHz ). For example, the dual-channel memory of DDR 400 can meet the CPU of fsb800, And the DDR2 533 dual-channel memory can meet the CPU of fsb1066. The DDR2 667 dual-channel memory can meet the CPU of fsb213, DDR2 800 memory dual-connection can meet fsb1600.

At present, the core CPU is still fsb800 at the low end (Mutton Goat 420, e2140, e4300, etc ), at this time, a DDR2 667 memory can not meet the requirements of the CPU (if the frequency reaches 800 ), one DDR2 800 memory can meet your needs (or two-channel ddr400 and two-channel memory groups, but there are very few such boards ).

If the frequency is too high, for example, e2140, when the external frequency of the CPU is from 200 to 266, the FSB is 1066. In this case, the dual-channel DDR2 533 can meet the bandwidth requirements, when the frequency reaches 333, the dual-channel 667 can meet the bandwidth. When the frequency reaches 400, the FSB is already 1600, and only the dual-channel DDR2 800 memory can meet the CPU requirements.

It can be seen that, if the fsb800 series is not frequently used, it is best to start with a single 800 of memory. If the purchased fsb1066 or 1333 U, the single memory will not be able to meet the requirements completely, it is best to use dual channels. If you want to overclock, for example, the 400 outer frequency that everyone dreamed of, it is best to buy two 800-Bit Memory at a time to form a dual-channel. Otherwise, even if the CPU usage goes up, the CPU will be dragged back due to insufficient memory bandwidth. Currently, the price of 800 memory and 667 memory is almost the same, so we should not consider 667 memory.

FSB of some CPUs!
Fsb800 sai Yang 4xx series, Pentium e2xxx series, core e4xxx series, and very old Pentium D series. 9 S % p4
Fsb1066 part e6xxx series (6300/6400/6500/6320/6420), e7xxx series (7200/7300), X6 (x6800), 4-core q6xxx series columns (6600/6700 ).
Fsb1333 part e6xxx series (6550/6750/6850), e8xxx series (8100/8200/8300/8400), 4-core q9xxx series (9100/9300/9550)/qx9xxx (9650)/qx6xxx (6850 ),

Supplement: Recently, it was found that the old diyer used the e7200/e8300 CPU, but only one DDR2 800 memory, which would seriously drag down the system. Avoid installation during installation.

Note: For amd CPUs, memory is integrated internally.ManagementSo you do not need to go through the North Bridge to read the memory data, but the CPU directly reads the data. Therefore, unlike Intel's CPU, You need to emphasize the bandwidth allocation problem, generally, a single 2G DDR2 800 can be used for installation.

If you do not know the CPU and memory bandwidth of your system, you can run a software called Everest to check the bandwidth of the two users under "motherboard"-"motherboard. As long as the memory bandwidth is higher than the bandwidth of the front-end bus (FSB.

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