Memory Timing

I currently have 2 gigs of corsair XMS2 PC 6400 ddr2 ram at 800 Mhz. I think The timing is 5-5-5-18. Here is a screen shot of the CPU-Z memory Page.


First off, CPU-Z says that my ram is operating at a DRAM frequency of 405 MHz, does this mean that each stick is operating at 405 MHz for a combine 810 MHz, or is my ram running at half speed?

I was considering upgrading my ram, and most of the corsair xms2 sticks I can find are operating at 4-4-4-12. Is it okay to mix ram timings?
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  1. no it means both of your sticks are operating at 810Mhz individually...but cpu-z only shows the real frequency which is 405 MHz for both modules..And the effective frequency for both modules will be 810Mhz.

    No dont mix rams with differnt timings and frequency as the resultant timing would be
    5-5-5-18 and not 4-4-4-12
  2. thanks for the reply. So if I were to upgrade my memory, I would want to buy the ram with the 5-5-5-18 timing because if I did pair it with memory with a timing of 4-4-4-12, both sticks would operate at 5-5-5-18 anyways?
  3. Yes. Generally, when you mix memory timings, your memory will run at the speed of the slowest component. If you increase the RAM voltage, you might be able to tighten the 5-5-5-18 timings a little.

    Several years back, when I build my first Core2 system (eVGA 680i, E6600), I did a lot of testing. Going from 5-5-5-15 to 4-4-4-12 increased my memory i/o by about 2 1/2%. But improvement in total system performance was negligible.
  4. nukemx5 said:
    thanks for the reply. So if I were to upgrade my memory, I would want to buy the ram with the 5-5-5-18 timing because if I did pair it with memory with a timing of 4-4-4-12, both sticks would operate at 5-5-5-18 anyways?


    If you want to more about memory then see the following links:
    http://www.hardwaresecrets.com/article/152
    http://www.hardwaresecrets.com/article/26
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