NVIDIA Quad-SLI with the ASUS EN9800GX2

Name: NVIDIA Quad-SLI with the ASUS EN9800GX2 - Page 2
Brand: NVIDIA

by Marco Chiappetta — Tuesday, March 25, 2008, 09:00 AM EDT

To implement Quad-SLI with a pair of GeForce 7950 GX2 cards, NVIDIA developed a rendering mode designed to leverage the power of the four GPUs powering the cards.

Typically, multi-GPU scaling is achieved by using either AFR, for Alternate Frame Rendering, or SFR, for split frame rendering. For older GeForce 7950 GX2 Quad-SLI configurations NVIDIA combined these two modes of operation and created AFR of SFR. What this mode did was take alternate frames and split the frames for rendering across the four GPUs. SFR, however, doesn't scale as well as true alternate frame rendering and SFR isn't universally compatible either. SFR also usually has more communications overhead and applications with a heavy vertex workload don't benefit as much.

With a pair of GeForce 9800 GX2 cards, however, NVIDIA is now able to use AFR in many games for better scaling across the GPUs. AFR is the preferred mode because all of the 3D rendering workload is parallelized (pixel fill, raster operation, vertex transform, etc.) and each GPU can work on its own frame. AFR is not universally compatible with every application, but when it does work, performance is usually increased significantly.

Tags: Nvidia, Asus, sli, X2, 980, N9, id

Marco Chiappetta

Marco's interest in computing and technology dates all the way back to his early childhood. Even before being exposed to the Commodore P.E.T. and later the Commodore 64 in the early ‘80s, he was interested in electricity and electronics, and he still has the modded AFX cars and shop-worn soldering irons to prove it. Once he got his hands on his own Commodore 64, however, computing became Marco's passion. Throughout his academic and professional lives, Marco has worked with virtually every major platform from the TRS-80 and Amiga, to today's high end, multi-core servers. Over the years, he has worked in many fields related to technology and computing, including system design, assembly and sales, professional quality assurance testing, and technical writing. In addition to being the Managing Editor here at HotHardware for close to 15 years, Marco is also a freelance writer whose work has been published in a number of PC and technology related print publications and he is a regular fixture on HotHardware’s own Two and a Half Geeks webcast. - Contact: marco(at)hothardware(dot)com