6870 crossfire bottleneck 965?

[KoreanOnE]

I just bought another 6870 to crossfire and I think it's bottlenecking... I had better performance on one than I have two. On crossfire, there are a lot of lag and stutters. Even some tear in the graphics. This happens on Medium - Ultra settings. There are no differences. Even freezes my mouse at times.

I tried overclocking the cpu to 3.8ghz and the FSB to 2600mhz and no performance change.

I removed all drivers and reinstalled the latest Catalyst 11.11 and still not better than a single card setup.

Help? Before I go and buy a 6-core or even an i7.

My system specs are as followed:

CPU : AMD 965 3.4ghz
Motherboard: ASUS
Memory : 8 GB Corsair Vengeance
HD: 1 TB Seagate, 750 WD Caviar Black
PSU: Antec 750W
Video: 2x ASUS Directcu 6870

 

[simon12]

Whether the CPU is a bottle neck or not I don't think its whats causing the problem. Check what temps you are getting on the CPU & GPUs, if that all looks OK try both the cards individually. Also does this happen in every game? And what resolution are you using?

 

[rolli59]

It is not a bottleneck, so to say! Looks like you are experiencing micro stutter http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html and the screen tearing happens if V sync is not enabled when the GPU's are trying to render more frames than the rest of the system can deal with.

 

[Baralis]

You could monitor your GPU usage. I use MSI afterburner to monitor mine. If you are not seeing high GPU usage it could be a good indicator of a CPU bottleneck. In high CPU dependent games I will see a bottleneck with my unlocked Rana 445, it cannot fully push my 6850. GPU dependent games it all comes down to my GPU and will show by being continuously maxed out during play.

 

[simon12]

I think the problem sounds far to serious to be micro stutter and even if there is a major bottleneck it will not cause performance to be worse than a single card.

 

[jsrudd]

What game are your playing? Could be that the drivers are terrible for crossfire. I remember something like this happening to me with fallout NV.

 

[Uther39]

I gave up on the whole SLI, Crossfire game exactly for the reasons you state in your system issues, i constantly suffered from stability and graphic glitches with both SLI and Crossfire, now i just buy single high end cards 6970/GTX580 etc etc, and have no such issues