RAM vs CPU Freq

[deadfolk]

Hi all,

Can someone please explain (or point me in the direction of an existing post) the relationship (if any) between the frequency of RAM and the frequency of the FSB/CPU? The stickies don't seem to address this, and are also a little out of date, I think.

e.g. I have a CPU running @ 3.3Ghz on (9x367). My RAM is rated as PC2-8500 (1066Mhz).

Are the CPU and RAM numbers tied together somehow, or do you clock them independently? If I up the speed of the CPU, do I have to do the same to the RAM? And how do I know calculate how fast the RAM is going to run?

Thanks for any info.

 

[Temi_D]

CPU and RAM frequencies are linked. The FSB is the base frequency of the CPU which is the multiplied by the multiplier (x9 in your case) to get the true speed, and the RAM frequency is linked to the FSB by ratios.

I will use your cpu as an example.

The FSB is 367MHz and the multiplier is x9 so the true speed is 367 x 9 = 3303MHz

Because the FSB is 367 if your FSB : DRAM ratio is say 1:2, Then the DRAM speed is 734 and since its DDR2, the effective ram speed is 734 x 2 = 1468. Your ram is rated at 1066Mhz, so the optimal FSB : DRAM will be 2:3 which will result in an effective ram speed of 1101MHz.

Before you up the speed of your cpu, you will need to know your FSB : DRAM ratio. You can download cpuz, it tells you under the memory tab. so you might need to reduce the ratio if you plan to increase the overclock.

btw what cpu and motherboard have you got?

 

[deadfolk]

That's an excellent explanation. Thank you for taking the time.

To answer your question, my CPU is Q6600 and the board is a Asus P5Q Pro Turbo.