Verdict: SLI Iin any motherboard
So far, SLI has pretty much been a long and disappointing battle, littered with underperforming hardware, a lack of support from game developers and the general feeling that the whole thing is a waste of everybody's time and money. After all, conventional wisdom would suggest that if dual graphics are such a good idea then why have all the consoles snubbed it? So, when the Asus EN7950 GX2 dropped into the office soon after the horrific mess that was Quad SLI, we were all prepared for the worst. It is, after all, a dual-graphics card that's horribly reminiscent of the cards powering the Quad PC. It couldn't have been met with lower expectations.
Imagine our surprise when we found that the Asus EN7950 GX2 isn't too shabby at all. Physically, it's a big card, although it's considerably smaller than the 7900 GX2 Quad SLI cards. It fits easily into the same double slot that's taken up by any graphics card with a big cooler. The two cards are equipped with small aluminium coolers, which, even when fully spun up, are acceptably quiet; this is a huge improvement over the racket caused by the 7900 GX2 cards. A single PCI-E power connection supplies both GPUs.
Each of the two GeForce 7950 GPUs is equipped with 24 pixel and texture processors,16 ROPs and 8 vertex pipes, and each GPU has a supply of 512MB of GDDR3 memory. The GPUs are clocked at 500MHz, while the GDDR3 memory runs at 600MHz (1.2GHz effective). These frequencies are fairly tame compared with the lavish speeds of a GeForce 7900 GTX, for example, but, given the lack of space on the PCB for large coolers, this is an understandable precaution, although it also has implications for performance, which we'll come to later.
The way in which the 7950 GX2 works isn't just a simple matter of cramming two GPUs together to get literally double the performance. In reality, it's two GPUs running together in SLI. Nvidia has been promoting specialised SLI core logic chipsets, such as nForce4 SLI, for nearly two years, and up until now, they've been required for running dual Nvidia graphics cards. However, Nvidia has removed this restriction with the 7950 GX2, thanks to the use of a PCI-E switch that acts as a bridge between the two GeForce 7950 GPUs. All a motherboard has to do in order to support the 7950 GX2 is be able to communicate with this PCI-E switch. For this reason, almost any motherboard with a 16x PCI-E slot should be able to support the 7950 GX2, although a BIOS update may be necessary. Nvidia publishes a list of motherboards that it's tested, which are certified to work with the 7950 GX2, at www.nvidia.com. In addition to the boards listed, we successfully tested the Asus EN7950 GX2 in an ATi CrossFire board, the Asus A8R32-MVP Deluxe, and a ULi M1695 board, the ASRock 939Dual-SATA2.
Disturbingly enough, the EN7950 GX2 is also equipped with its own SLI port, so you can use two of the cards together in Quad SLI. It also supports HDCP (High Bandwidth Digital Copy Protection).
PERFORMANCE
With a price tag of around £425, naturally, the most important aspect of the EN7950 GX2 is whether its performance measures up to the top-end single GPU cards. After all, the card is much more expensive than any single GPU card, but almost £300 cheaper than two 7900 GTXs. Like all SLI systems, however, it's forced to rely on only one GPU for games that don't have an SLI profile.
F.E.A.R. does have an SLI profile, and the EN7950 GX2 absolutely demolished the game. With a minimum frame rate of 34fps at 1,600 x 1,200 with 4x AA and 8x AF, and an average of 66fps, it provided around 30 per cent more performance than the X1900XTX or the 7900 GTX.
However, in games that don't have an SLI profile, performance sucks. Need for Speed: Most Wanted, for example, supports only a single GPU, with the result that the EN7950 GX2's performance fell well below that of the other high-end cards. A minimum of 30fps and an average of 41fps at 1,600 x 1,200 with high AA and high AF is still playable but, due to the EN7950 GX2's lower GPU speed and slower RAM, it's slower than a 7900 GTX.
That anomalous result aside, however, the EN7950 GX2 did silly things with Quake 4, much more so than with F.E.A.R. An X1900XTX can produce a playable frame rate in Quake 4 at 1,600 x 1,200 with 4x AA and 8x AF, but the minimum frame rate drops to 27fps in places. The EN7950 GX2, on the other hand, breezed through the test, averaging a stunning 58fps, and never dropping below 42fps. This makes the EN7950 GX2 by far and away the fastest graphics card ever in Quake 4. Even taking into account the fact that we now run the somewhat better optimised 1.2 patch for Quake 4, this is still a mighty impressive result.
Overclocking the EN7950 GX2 yielded modest improvements to the clock speeds, taking the core to 550MHz and the RAM to 700MHz (1.4GHz effective). However, the return on this comparatively small overclock was much better than we'd hoped, with the frame rates in our F.E.A.R. tests seeing sizable increases of between 10 and 20 per cent.
CONCLUSION
The EN7950 GX2 is almost good enough to undo 18 months of underachievement on the part of SLI. The quiet cooling allowed for by the comparatively low power requirements of the GPUs means that the card isn't nearly as abrasive as you might expect. Even with both GPUs in full use, the system demanded just 271W, which is substantially less than some single-GPU cards we've tested, such as the notoriously power-hungry Radeon X1900XTX.
Ultimately, the EN7950 GX2 is priced smartly enough that it isn't a freak, as it's much cheaper than two 7900 GTXs, and not much more expensive than two 7900 GTs. Of course, it only delivers top performance in games that have SLI profiles. However, if you have a high-resolution monitor, a compatible motherboard, and your favourite games are known for their love of all things SLI, then the EN7950 GX2 is the card you've always wished for.
