4850 Crossfire has lower than expected performance

[Eclipsa]

So I just set up my new system and ran some benchmarks..

First I only installed 1 GPU and ran 3dMark06..

My result w/ 1 GPU = 12,954
Tom's result w/ 1 GPU = 14,643

This didn't seem like a big enough difference to get worked up about.. The issue came when I installed the second GPU..

My result w/ 2 GPUs = 17,479
Tom's result w/ 2 GPUs = 23,553

I was wondering if anyone had any idea what might be causing such a big discrepancy in the scores when I am in crossfire?


My specs:

Windows 7 64-bit
2x Sapphire Radeon 4850 (512 MB, 256-bit)
AMD Phenom II X4 955 BE
Corsair 750 W PS
ASUS M4A79XTD mobo
Acer 1920x1080 23"
4 gigs Gskill DDR3

ATI Driver ver. 8.712.0.0000 (latest, dl from catalyst ctrl ctr)

Your help and/or thoughts will be greatly appreciated..

 

[mindless728]

is that the total score from 3dMark06, if os i think Tom's uses a core i7 for there tests (correct me if i am wrong)

 

[rolli59]

Overclock that CPU and try again. Tom has been known to use I7 975x @ 4.0 GHz lately, that will affect the score.

 

[Eclipsa]

I've never been able to find any system specs for Tom's graphics benchmarks (strange if you ask me)..

But does it make sense for the CPU to make such a big difference only in crossfire, and not in single GPU mode?

 

[jimmysmitty]

is that the total score from 3dMark06, if os i think Tom's uses a core i7 for there tests (correct me if i am wrong)

Yep Core i7 975X and now a Core i7 980X.

And yes it would make a difference with more than 1 GPU. From tests, the Core i7 CPU doesn't bottleneck a dual GPU setup as much as other CPUs do.

 

[rolli59]

I've never been able to find any system specs for Tom's graphics benchmarks (strange if you ask me)..

But does it make sense for the CPU to make such a big difference only in crossfire, and not in single GPU mode?

Its there in every article. http://www.tomshardware.com/reviews/radeon-5870-eyefinity6,2595-5.html
The more powerful a GPU the more apparent a CPU bottleneck becomes.

 

[Eclipsa]

Best answer selected by Eclipsa.