Memory for OC: DDR400 or more?

[kevinvives]

I am building an opteron 165 rig with an OC planned to 2.6-3GHz.

Its enough for achieve that results the PC3200(DDR400)? or Should I get DDR500 or so?
Raising the HTT is also raising the mem freq right?, but if the multiplier is unlocked in optys you don't need to modify the HTT no?
The DDR500 has higher latencies, so the freq advantage is negated by this?

sorry 4 my bad english

I have reading so much I can, but there are a lot of doubts yet.

 

[MrX8503]

the point of ddr500 is so that you can run it without dividers, but if you have ddr400 you have to run dividers because when you overclock the mem will go over its spec.

Latencies dont matter with a64 processors, also ddr400 would have high latencies too if it was ddr500 and vice verca.

 

[Madwand1]

There's a very interesting recent article on this in THG.

http://www.tomshardware.com/2006/03/31/tight_timings_vs_high_clock_frequencies/

I'd love to be able to sum it up for you here, but it's too complicated for that. OK, I'll try, but without any but very rough numbers (order of magnitude). Basically, memory speed and latency both matter, and both scale with CPU speed. I.e. at lower CPU speeds, the memory speed and latency matter less (because they're less of a bottleneck to the overall process).

The order of magnitude is around 10% performance improvement for doubling of the effective RAM speed, and around 5% performance improvement going from C3 to C2. Again, please read the article for much more on this -- my figures are nice round simplifications for illustration.