The first attempt to build a four-processor consumer-class graphics subsystem undertaken by Nvidia was unsuccessful, to put it mildly. We used a ready-made platform from a system integrator who had been granted permission to sell quad-SLI complexes, yet the tested system was far from stable (for details see our article called Quadtet: Nvidia GeForce 7900 Quad SLI Performance Unveiled). Besides the stability issues, its performance wasn’t as high as we had expected whereas the image quality was horrible in some games due to various visual artifacts. That implementation of the quad SLI concept proved to be almost unusable.
Still, the concept itself definitely has a potential and may achieve what is impossible on dual-processor tandems, let alone single-chip graphics cards. And of course Nvidia didn’t stop to promote the new technology, especially as they had promised that gaming quad-SLI systems would eventually be available for integration by users themselves, not only as ready-made solutions. And now this time has come.
Theoretically, it became possible to build a four-processor graphics subsystem in your home computer about two months ago. It’s when the clumsy and very unreliable GeForce 7900 GX2 graphics card that had been used in the first-generation quad SLI was transformed into a rather compact and simple GeForce 7950 GX2 (for details see our article called Two for One: Nvidia's Dual-Chip GeForce 7950 GX2 Reviewed). Even with certain drawbacks, that card became a sensation among single-PCB solutions, delivering unrivalled performance and image quality. The latter was achieved by offering full-screen antialiasing modes that had previously been unavailable on classic single-chip cards.
However, the option of uniting two GeForce 7950 GX2 cards into a quad SLI subsystem was blocked by Nvidia on the driver level. The company thought it was too difficult for the end user to assemble such a subsystem on his own. There was some logic in this thinking. Until the arrival of the GeForce 7950 GX2 Nvidia could argue that:
- A quad-SLI graphics subsystem consumes a lot of power and system integrators can take care that it receives what it needs
- Having a very dense component layout, a quad-SLI subsystem requires good ventilation inside the system case. System integrators can find an optimal balance between the ventilation quality and the level of noise
- The integrator’s support service can help owners of quad-SLI systems in case of some problems
But the first point can now be criticized because one GeForce 7950 GX2 consumes about 110-120W which is comparable to the power draw of a single Radeon X1950 XTX. So, two such graphics cards will require about as much power as a Radeon X1950 XTX CrossFire subsystem and will not need a special power supply. Any high-quality 600-650W power supply will do. Still, Nvidia insists on higher numbers. The power supplies it has certified so far all have a wattage of 700W and higher (you can read the full list on the appropriate page of the SLIZone website).
The second point isn’t as urgent as it used to be, too. The GeForce 7950 GX2 is much smaller than the GeForce 7900 GX2 and can be easily installed into almost any standard ATX system case. Of course, the case must be ventilated well, but this rule applies not only to quad-SLI subsystems based on two GeForce 7950 GX2, but also to any high-performance SLI or CrossFire subsystem. The ventilation issues aren’t any news for an experienced home user. What may become a problem when a quad-SLI platform is assembled at home is that the GeForce 7950 GX2 may turn to be incompatible with the mainboard.
Thus, the only argument in favor of purchasing a ready-made quad-SLI system from an authorized system integrator is that you are given a warranty and provided the manufacturer’s tech support. However, this won’t help avoid performance or compatibility issues that must be solved by Nvidia as the developer of SLI technology and writer of the appropriate drivers. It seems that quad SLI wasn’t that difficult to implement on the hardware level, but had a lot of problems with the software as was shown in our preview.
On July 20, 2006, Nvidia finally removed the barrier and released its ForceWare 91.37 driver that would allow using two GeForce 7950 GX2 cards in a quad-SLI subsystem. That version of ForceWare was to come with ready-made quad-SLI systems but for some reason had a beta status and was not officially supported by Nvidia. So, it’s only on August 13 that the limitation on building users’ own quad-SLI subsystems was removed – the company released ForceWare 91.45 which had a lot of corrections to solve the known problems of quad-SLI. You can read the list of changes by downloading the release notes. Right now, ForceWare 91.47 is the latest version of the quad-SLI-supporting driver from Nvidia, and we used it for this review.
We’ve recently obtained a second sample of the GeForce 7950 GX2, so we can now check out what performance and compatibility improvements have been brought by the new driver for quad SLI. Will we indeed be lifted up to an unrivalled level of performance in games? Let’s first recall the basics of Nvidia’s quad SLI technology, though.