XFX GeForce 9800 GX2 Quad SLI Versus ATI CrossFireX

XFX GeForce 9800 GX2 Quad-SLI Testing

Last week, we got a chance to look at the XFX GeForce 9800 GX2 graphics card and found that it was a very powerful card for gaming. At the conclusion of that article we stated that we couldn’t show Quad-SLI numbers as NVIDIA had them under NDA. The gag order has finally lifted, so we can share with you our thoughts on Quad-SLI with a pair of XFX GeForce 9800 GX2 graphics cards and, of course, we also have a pair of ATI Radeon HD 3870 X2 graphics cards for some Quad-CrossFireX testing to go along with them.

Since we have already reviewed the Radeon HD 3870 X2 (here), the GeForce 9800 GX2 (here) and CrossFireX (here), we can move right on to the good stuff.

It’s been nearly two years since NVIDIA has produced a dual PCB video card design and they feel they have a winner in the works with the GeForce 9 series. One of the reasons NVIDIA feels so strongly about the GeForce 9800 GX2 is because they have a whole new approach at how the video game frames are being rendered. The first generation Quad SLI technology seen on the GeForce 7950 GX2 back in 2006, used a hybrid mode of split frame rendering (SFR) and alternate frame rendering (AFR) to enable concurrent rendering on four GPUs. With the latest games utilizing complex shaders, inter-frame effects, and multi-pass rendering, SFR becomes less efficient.

The GeForce 9800 GX2 features a new video bridge and a re-architected driver to allow for four frames to be rendered concurrently, but there is a catch. The OS framework required to support four frames in-flight is only available in Windows Vista. With the new 4-way AFR technique, geometry, texture, and shader processing all benefit from GPU scaling. Just how much does it scale? We will get to that in a second!

To get Quad-SLI enabled, we just added a second card to the system and went to the NVIDIA control panel to set the SLI configuration. After a few flickers and flashes, the software enabled Quad-SLI and we were able to reboot the system and get testing.