Re: Enabling SLI causes slow 2D and high CPU load
I too am experiencing similar issues with SLI. It sometimes works decent, although it introduces noticeable tearing in compiz with enhanced zoom. (I think it has something to do with SFR mode which I use because it seems to be the most stable.) But after a certain period of time which seems random, the screen will take forever to render, up to ten seconds or more and then becomes responsive for a second or two and becomes unresponsive again.
Another issue which happens fairly often is the bottom two thirds of the screen will become garbled after using vdpau or project-m music visualizer and other fullscreen applications. Using compiz will always cause the screen to update properly until another fullscreen application is exited. This does not always happen though, maybe 50% of the time it will. I use 3 GTX480 with SFR, I have never really tried with AFR as it seems much slower with compiz. I have experienced this issue without SLI enabled, so it may not be related.
When the computer does become slow or completely unresponsive, I Alt + PrntScrn + R, E, L, S, U, B to reboot and often times the computer will boot up and do the same thing again right from login. After another reboot the problem disappears (for another random period of time, at least a few hours usually.)
2D applications are the most noticeably hit by the performance loss of using SLI. 3D is slower as well, from what I find. Games are noticeably choppier with SLI. I believe the 2D and 3D slow acceleration has something to do with my unresponsiveness issue.
I am currently using driver version 275.21 because the 280.xx driver series seems to break SLI for me. When I boot using SLI and 280.xx drivers, the computer is completely unresponsive as soon as any compiz effect is used. I have not tried the latest 280 series driver, I will try it soon and report back.
Edit: just started on 285.03, seems really good so far, 3D performance seems ok, as well as SLI performance compared to older drivers, although in unigine benchmark at 1080p extreme tesselation I get 8 fps to start and it stays low. In windows it would be at least 60 Fps. Just tried 275.21 with and without SLI I get 20 FPS in unigine. Must be some sort of regression there.
Edit 2: Less than an hour, first hard freeze on 285.03. in SFR. I get the same FPS in unigine with SLI enable or disabled as well ,I have just found.
Last edited by cheechr1; 08-21-11 at 08:11 PM.