Nvidia reintroduced SLI two years ago, but the company found that two GPUs in a single system just wasn't enough. Four would be better. The GeForce 7950 GX2, Nvidia's newest video card, now makes two GPUs a mere starting point. The GeForce 7950 GX2 is a single card, but it comes with two GPUs and twice the amount of RAM found on normal video cards. Since the GX2 is a single card, you can place two in an SLI system for quad-GPU action. Welcome to the land of excess.
The GeForce 7950 GX2 sports two GeForce 7900 series GPUs; the single card has a combined total of 1GB of GDDR3 RAM, 48 pixel pipelines, and 16 vertex shaders. Nvidia reference specifications have the dual cores clocked at 500MHz and pegged the memory at 600MHz. The core clock of the GX2 is 200MHz slower than a GeForce 7900 GTX--but when you have two GPUs on a single card, who's complaining? According to Nvidia, heat output and power consumption forced the decision to ease off on some of the settings to ensure proper operation. However, the conservative engine speed gives the card manufacturers the opportunity to customize cards to offer higher clock speeds. The XFX GeForce 7950 GX2 we tested ships with a 570MHz engine clock, and 700MHz memory.
The double-wide GeForce 7950 GX2 will work with just about any motherboard that has PCI Express slots; check Nvidia's site for a complete list. You'll also need a quality 400W power supply to keep the card well fed, but you might need more juice if you go above reference settings. XFX recommends a 500W supply for its overclocked GeForce 7950 GX2.
If you manage to get your hands on two GeForce 7950 GX2s, you can run them in a single system to enable Quad SLI mode. However, for the foreseeable future, Quad SLI configurations will only be available only through system builders. Of course, we don't imagine that Nvidia would cripple retail boards from running in Quad SLI mode, and no one's going to stop you from buying two cards and slapping them in your system. If you plan to do so, make sure your motherboard is verified to run in Quad SLI mode, and be sure to have, at the very least, a high-quality 600W (our recommendation) power supply.
The XFX GeForce 7950 GX2 is the fastest single-card graphics we've had the pleasure to test here at GameSpot. Our XFX GX2 beat out the GeForce 7900 GTX and the Radeon X1900 XT in every single test. The XFX GeForce 7950 GX2 even manages to come close to our GeForce 7900 GTX SLI and Radeon X1900 XT CrossFire rigs.
We managed to get two GeForce 7950 GX2s running in our test bed without a hitch, and enabling Quad SLI mode proved trivial. Via the normal driver interface, we flipped a switch and were on our way to a system powered by four GPUs. Unfortunately, performance proved unimpressive and contained graphical errors; we mainly attribute that to the immaturity of the drivers. We're sure that, given some time, Nvidia can make Quad SLI a competitive solution.
With an MSRP between $599 and $649, the GeForce 7950 GX2 isn't a mainstream graphics solution, but it offers performance comparable to much more expensive dual-card SLI and CrossFire setups.
System Setup: AMD Athlon 64 FX-60 CPU, Asus A8N32 SLI Deluxe, Asus A8R32-MVP Deluxe Motherboard, 2GB (1GB x 2) Corsair XMS Memory, 160GB Seagate 7200.7 SATA Hard Disk Drive, Windows XP Professional SP2.
Graphics Cards: XFX GeForce 7950 GX2 570M XXX, GeForce 7900 GTX, Radeon X1900 XT.
Graphics Drivers: ATI Catalyst 6.5, Nvidia ForceWare 84.21, Beta Nvidia driver (for GeForce 7950 GX2).