XFX GeForce 9800 GX2 Quad SLI Versus ATI CrossFireXTue, Mar 25, 2008 - 12:00 AM
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.
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.