Crossfire cpu bottleneck?

[fizzy]

Hi,

I've been trying to get a bit more "oomph" out of my gaming rig. Its a twin ati x1900xt crossfire setup, using an asus board.

I ran 3dmark06, got a score of around 8600. Overclocked my gfx cards using the ati overclocking options - it stayed pretty much the same.

Reverted gfx overclock back and slowly overclocked the cpu to a stable max, and now getting around 9300. Again tried overclocking the gfx cards, but no real difference.

I can only think of two reasons - either the overclocking options in the ati drivers isn't actually having any effect, or its a cpu bottleneck. Anybody know at which point/speed does the cpu not become a bottleneck on a x1900 crossfire setup?

 

[fizzy]

Well, that would just prove that the cpu is not fast enough for the cards. I'm trying to find out what speed cpu needs to be to max out/keep up, rather than just realising I could have easily managed with two cheaper cards..

Ati drivers by default don't allow underclocking, so I guess I would need to use atitweak or similar instead...?

 

[fizzy]

Hmm... upping the AA/AF sounds like a good idea. That would put far more work the gfx cards way, which would the benefit of looking nice too...

Getting pretty decent frame rates on oblivion at 1920x1600 in outside areas too - although the FPS app seems to make it crash a lot more often.

My CPU is an amd x2 4600, currently clocked from its default of 2.4 to 2.76. I ran 2.83 for a bit, but one of the cores wasn't prime95 stable (although I haven't messed with voltages etc yet). Gonna need a very, very beefy cpu if its the bottleneck...? Better start tweaking my memory too I think...