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Is memory performance dependent on the cpu speed, NB, HT, or bus speed? Will a faster CPU yield better memory performance (for example in windows experience index).

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Yes and No. In most Intel consumer desktops, memory speed is locked at a specific ratio to the base clock speed, and the CPU is also locked at a ratio to that base clock speed.

If you overclock your memory by boosting the base clock speed, or by changing the memory multiplier, the memory will run faster.

Faster processors generally have the same base clock speed with a higher CPU multiplier, so the memory is still running at the same speed. If you overclock by boosting the CPU multiplier, then memory will stay the same. If you overclock by boosting the base clock speed, then both memory and the CPU will increase in tandem.

For example, my system is a 3.4GHz Core i7 with 332GB of RAM @ 1600MHz. The base clock for my system is 100Hz.

If I bump the CPU multipler from 34x to 44x, then my CPU will be running at 4.4GHz, but my memory will still be running at 1600MHz.

However, if I leave the CPU multiplier at 34x and bump the base clock to 200Hz, then my memory will run at 3200Hz and my CPU will run at 6.8Ghz. Both will then proceed to explode and release all their magic blue smoke.

(The numbers presented are only references for the core i7 and later generations, but the general concepts still apply. Prior to that, the FSB was the "base clock", more-or-less)

(I think AMD systems function similarly, but don't know for sure.)

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The explosion is likely to occur as a consequence of increased voltage, not increased frequency. (Increasing frequency and not voltage leads to instability, so most overclocking will increase voltage also) –  Ben Voigt Jan 28 '13 at 22:52
    
@BenVoigt Indeed! I guess I forgot to point out all the technical nuances of the joke :P –  Darth Android Jan 28 '13 at 23:15
    
Great explanation, but can you explain why my windows experience index for memory goes up with a faster cpu? –  agz Jan 29 '13 at 0:24
    
@agovizer It's entirely possible that the particular memory test that Windows Experience Index uses is CPU-bound; That is, your CPU doesn't have enough power to run the test fast enough to actually measure the Memory (Which could mean either a slow CPU or really fast Memory); That's just a guess though, I don't know the details of how the test is implemented. –  Darth Android Jan 29 '13 at 5:08
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