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Quad SLI: GeForce 7900 GX2

NVIDIA's SLI has been generally perceived as a success by those who follow the graphics industry. Nobody expected the revival of dual-cards that followed the introduction of the 6-series back in 2004, but SLI seems to have captured the imagination of enthusiasts everywhere.

The dual-card message has been a strong one for NVIDIA, and not just for its graphics cards - the add-one-later possibility means that it has shipped an awful lot of SLI compatible motherboards, too.

However, in recent months, SLI has been trumped by the latest revision of ATI's CrossFire technology. CrossFire launched last year with a whimper rather than a bang. The initial implementation using Radeon X850 CrossFire cards and CrossFire Xpress 200 (RD480) motherboards were notoriously buggy and performed poorly. However, the Radeon X1900-series cards fixed a lot of the problems with RD480 and RD580-based motherboards are now available too. Many consumers are finding that CrossFire will give great performance (although our own experience has varied, as we'll explain).

Of course, the graphics wars continue ever-onward, and at the Consumer Electronics Show this year, NVIDIA previewed a new technology - Quad SLI. Rather than just dual cards, Quad SLI would, as you might expect from the name, use four cards to deliver even more gaming performance. Dell was chosen to show off the new technology, and we took a few snaps with our Vegas SpyCamâ„¢.

The Theoreticals

Today, Quad SLI is finally shipping to the consumer, and we've got our hands on a retail system that has been built by an NVIDIA approved supplier. What we wanted to know was obvious - does it really work, and is it worth it?

More than that, there were a number of hypotheses that we wanted to come to a conclusion on, based on the tech specs of NVIDIA's Quad SLI technology.

Firstly, at what point does four graphics cards really become useful? As you will know, SLI doesn't give literally double the performance of one card, since the load balancing required to get the cards to work together properly creates an overhead. Where the graphics cards aren't being taxed by the in-game visuals, that overhead can eat into the framerate. So, with four cards worth of overhead, what kind of graphics load is required to actually get benefit out of Quad SLI? How hard do you have to push the resolution and image quality to be able to beat standard SLI performance and does it still remain playable at those settings?

Secondly, will this offer any kind of value to the consumer? Four high-end video cards can cost an awful lot of money, and a consumer is going to want a pretty damn good experience to justify that kind of purchase. Will Quad SLI be able to step up to the mark?

With those questions in mind, let's take a look at the technical details of Quad SLI.

Quad SLI: GeForce 7900 GX2 Introduction