More SLI trouble

I enabled SLI as "alternate frame rendering 1" mode. This is important later.

Ok, so after all of the driver drama I enable SLI and loaded up Crysis. And I have so say I was not all that impressed with the performance and I had expected I would be with SLI.

There was also weird rolling greenish flicker over the whole screen. Needless to say I was less than impressed. I loaded FEAR and set it up for SLI and the same thing happened.

Same green rolling flicker. I could not capture it with screen capture. When I tried it always looked fine. It was almost like the refresh was too slow. Like when you look at a CRT television on a home video, where you can see the refresh.

Anyway this was a major bummer. Anytime I enabled SLI I got this weird flicker. There are a lot of people with this problem on the forums, but not may answers that I could find. Games ran find on 1 GPU but really poorly with 2.

I decided on a whim to try split frame rendering (where one card does the top, and another does the bottom of the screen) to see what that looked like. To my amazement the top half of the screen was perfect.

But the bottom half was all distorted and ugly and green. My second GPU was messing up!

When using alternate frame rendering, viewing the distortion every other frame looked like a flicker to the human eye.

So now I had tracked down the source of the problem, but why was my second GPU messing up? This was a major bummer.

I thought maybe I had a bad video card, so I pulled out the known good one, and swapped the second one to the first slot and loaded the system with just the one card. And it was fine. The computer worked perfectly with the one card in it.

So, I put the other card back in position 2. So now the cards were switched on the motherboard and the problem cropped back up again. Now I suspected the second GPU was being starved for power.

That shouldn't happen though, I've got an SLI ready PSU with 700 watts of power. Or do I?