CAS vs. FSB

[DuckOnBike]

Because of a variety of OCing choices, I'm faced with this question: should I 1) - run my ram at CAS 3.0 at 200Mhz or 2) - run my ram at CAS 2.5 166 Mhz with a FSB divider on my OCed Athlon or 3) - run my ram at 166 with no divider, thereby dropping my processor overclock.

Thoughts?

[Kaso]

You should always try to run athlons on 1:1

[I.M.O.G.]

Run at cas 3 200 mhz... A considerable FSB increase of 30+ mhz has been shown to provide more improvement than running a lower CAS. Ideally, you would want to run at cas2.5 200mhz of course. :)

[johan851]

Use a benchmarking program to see which configuration is better for your system. This one's an easy call, but other ones might be tougher.

There's also a lot more to RAM timings than CAS latency - tRCD and tRP are more important than CAS in DDR memory. Read the stickies at the top of the memory forum for more info.

[mrspec3]

Run at cas 3 200 mhz... A considerable FSB increase of 30+ mhz has been shown to provide more improvement than running a lower CAS. Ideally, you would want to run at cas2.5 200mhz of course. :)

What he said

[DuckOnBike]

... tRCD and tRP are more important than CAS in DDR memory.


Actually, I had a question about that too: does it make any sense to have one of these numbers lower than the other, or should they always be equal? I can get my tRP to 2, but I can't get the tRCD lower than 3.

[johan851]

Yeah, that's pretty common. Most IC's other than BH-5, BH-6, and mT -5BC have trouble running a tRCD of 2. tRCD has the most effect on performance - that's why those chips are so popular. They don't have to be equal by any means, running at tRP of 2 and tRCD of 3 is fine.

[DuckOnBike]

Thanks for the explanation, Johan.

[I.M.O.G.]

Bah, I'm getting rusty... Welcome to the forums Duck, we're glad to have you with us! Have a click on my sig if you want to pop your head up and say hello to everyone. :)