Multi-GPU graphics

ATI and Nvidia would have you believe that you need several graphics cards to get the best gaming experience. To find out, we put SLI and CrossFire systems to the test.

Nvidia 512MB GeForce 8800 GTS

Manufacturer:	Price:
NVIDIA	£160 inc VAT
Reviewer:	Review Date:
James Gorbold & Phil Hartup	Nov 1999

	OVERALL RATING

SCORE

Not Rated

Verdict: A single 512MB 8800 GTS is great, but a pair struggle to prove their worth.

If Nvidia were a supervillain, we'd suggest the moniker 'Master of Confusion', due to its propensity for releasing the same GPU under different names, and different GPUs under very similar names. For example, the 512MB 8800 GTS has little in common with the 320MB and 640MB 8800 GTS, as it's based on the G92 GPU, while both the latter cards are based on the earlier G80 GPU.

This means that despite its mid-range price and smaller frame buffer, the 512MB 8800 GTS is a lot more advanced than the 640MB 8800 GTS. For example, the former had 96 stream processors running at 1.2GHz, while the 512MB 8800 GTS has 128 stream processors clocked at a faster 1.625GHz. The GPU core in the 512MB 8800 GTS also runs faster, at 650MHz as opposed to 500MHz. As its name suggests, this card features 512MB of GDDR3, which runs at 970MHz (1.94GHz effective) and is connected to the GPU via a 256-bit memory controller. The G92 architecture also means that the 512MB 8800 GTS is much more power-efficient than its predecessors, consuming only 10W more power than the 320MB 8800 GTS, yet running many games nearly twice as fast.

The 512MB 8800 GTS is fitted with a dual-slot cooler that's much quieter than the single-slot screamer fitted to the 8800 GT, which was released within a few days of this card. A single 512MB 8800 GTS proved to be a solid performer in most of our test games, producing a smooth frame rate at 1,680 x 1,050 in Call of Duty 4, Oblivion, Team Fortress 2, S.T.A.L.K.E.R., DiRT, Need for Speed: Pro Street and Company of Heroes: Opposing Fronts; in some cases, this was true even at 1,920 x 1,200, a commendable achievement for a card retailing for a good deal less than £200.

Two-card SLI

As with all the SLI configurations, we discovered that adding a second graphics card doesn't make every game run twice as fast. For example, Crysis, one of the few games that the single 512MB 8800 GTS couldn't quite handle, appeared to ignore the existence of the second card completely, and ran at virtually the same speed when SLI was enabled.

Oblivion ran slower with SLI enabled, with the minimum frame rate dropping by around 10 per cent at both 1,680 x 1,050 and 1,920 x 1,200, something we experienced with many of the SLI systems. If you insist on running two 512MB 8800 GTS together in SLI, we'd definitely recommend disabling SLI in the Nvidia Control Panel before launching ArmA, as the game's minimum frame rate dropped by an astounding 71 per cent with SLI enabled at 1,920 x 1,200, and 55 per cent at 1,680 x 1,050.

Call of Duty 4, S.T.A.L.K.E.R. and Team Fortress 2 responded much better to the second graphics card, speeding up considerably when SLI was enabled. However, given that a single 512MB 8800 GTS is powerful enough to run all three games with a smooth minimum frame rate (25fps or more) at 1,920 x 1,200, you have to ask how much you benefit by spending £160 on a second 512MB 8800 GTS. Sure, a higher frame rate is always welcome, but it isn't worth paying an extra £160 if your games already run smoothly.

Our two racing games, Need for Speed: Pro Street and DiRT, were welcoming towards the second graphics card too. However, in terms of playable minimum frame rate, SLI merely buys you the ability to play DiRT smoothly at 1,920 x 1,200 - hardly a stunning return for a £160 investment, plus an additional 122W of power consumption and a noisier PC.

As with other Nvidia graphics cards, neither Supreme Commander nor Company of Heroes: Opposing Fronts proved SLI friendly. Both game's minimum frame rates plunged when two graphics cards were brought into play. Supreme Commander's minimum frame rates were low to start with and became even lower with SLI (a 50 per cent drop, from 6 to 3fps), but CoH's plummeted from a strong 53fps to a woeful 10fps with a second graphics card.

Strangely, the 9800 GX2 - which is essentially two 512MB 8800 GTS stuck together but with a different ForceWare driver - didn't exhibit any of these problems in either strategy game. Clearly, if you're an armchair general who favours strategy games over first-person shooters or driving games, running two 512MB 8800 GTS cards in SLI would be the most idiotic strategic move since Hannibal won the battle of Cannae and then decided to pitch his tent and not attack Rome.

Conclusion

Our experience of playing ten different games at two resolutions on a pair of 512MB 8800 GTS is typical of SLI as a whole. A single 512MB 8800 GTS is capable of playing most modern games at a decent resolution, yet the games that have the greatest need for extra graphics power, ArmA and Crysis, either run slower or receive no benefit from SLI.

It isn't all doom and gloom for SLI, as some games do run faster - several by a significant margin - but if you already own a 512MB 8800 GTS, SLI isn't a compelling option, thanks to its faults. We'd recommend holding on to your 512MB 8800 GTS for a little while to see how well ATI and Nvidia's next generation of single-GPU cards perform, rather than buying a second 512MB 8800 GTS.

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