Quad SLI: GeForce 7900 GX2

GeForce 7900 GX2 cards up close

The GeForce 7900 GX2 is based on the same G71 chip that NVIDIA uses for its GeForce 7900-series desktop parts. The core has the same pixel and vertex shader array as all other G71-based cards, meaning a total of 24 pixel shaders, 8 vertex shaders and 16 pixel output engines.

Each GPU is clocked at 500MHz and has a total of 512MB frame buffer running at 1210MHz, allowing for high detail and high resolution gaming. The GPUs are stacked on separate PCBs, meaning that there are two PCBs per card. As discussed earlier, the GPUs are all connected together with SLI bridges capable of delivering 1GB/sec of data transfer.

Here is issue number one: the cards are absolutely massive. The PCB is a whopping 312 milimetres long, which means you could well face difficulties fitting them into your case. The cooler is an interesting design, designed to be thin enough to allow for enough airflow whilst jutted up against the back of another card.

The cards themselves don't give off a great deal of noise. The source of the noise in our test system was from the power supply unit. Tagan's 900W TurboJet unit - essentially two 450 watters bolted together in one box - gives off quite a howl when its running under heavy load. We wouldn't want to imagine how much noise its 1100W version emits.

Unscrewing one of the cards to separate the two PCBs reveals the inter-GPU connections on the card. There is a PCI-Express link, along with the SLI link between the two GPUs on each card. Obviously, data needs to be able to get through the two GPUs, yet only one of them is connected to the motherboard directly.

The larger of the two inter-PCB connectors is the PCI-Express link, while the smaller of the two is the SLI link between the two GPUs. This is in addition to the two SLI bridges that go across the cards.

The Scan 3XS Panther

The system we received our Quad SLI boards in was built by Scan. The Panther costs £4,271.11 inc VAT but without a monitor (see below).

The system is configured with an AMD Athlon 64 FX-60 CPU, the two GeForce 7900 GX2 Quad SLI cards, 2GB of Corsair XMS4000 memory, two 150GB Western Digital Raptors in RAID 0, an Asus A8N32-SLI Deluxe motherboard, a Creative X-Fi Fatal1ty FPS and a funky custom paint job.

There is the option to add noise dampening which we'd definitely recommend.

If you don't already own a high-end display to hook up to your spanky new Quad SLI system, Scan can sell you one. The monitor options include 17" and 19" Iiyama PL-series TFTs, a couple of 20" widescreen LCDs, the 24" Dell 2405FPW widescreen, the ViewSonic VP231WB 23" widescreen and the huge 30" Dell 3007WFP behemoth that we tested with. The latter is required for gaming at 2560x1600.