Verdict: Both the GT and GTS are underpowered.

The Nvidia GeForce 8800 GTS and 8800 GTX certainly have the power to please the crowds, but by far the highest volumes of graphics card sales are in the sub-£150 price range, so it was inevitable that Nvidia would release cheaper alternatives for those who want DirectX 10-compatible graphics cards without spending too much money. The cheap-as-chips 8500 GT covers the sub-£100 market, while the more expensive 8600 GTS and 8600 GT are positioned as mid-range cards.

Perhaps the most hotly anticipated of these cards is the 8600 GTS, as it was assumed that it would make the perfect partner for 17in and 19in TFT monitors, which have modest native resolutions of 1,280 x 1,024 or 1,440 x 900. However, as they're based on the new-fangled unified shader architecture, the performance of Nvidia's 8-series cards depends heavily on the amount of stream processors in the GPU. In short, the more stream processors a GPU has, the more powerful the card will be.

There's an obvious pattern to Nvidia's range. At the top of the pile, there's the 8800 Ultra, which is designed to provide gamers with high-resolution gaming at 1,920 x 1,200 on a 24in TFT and is equipped with a whopping 128 stream processors. The 8800 GTS, on the other hand, is aimed at those who game at less demanding resolutions and, as such, both versions of the card are equipped with 96 stream processors. The next logical step down from this would be a card aimed at the fairly ubiquitous 17in TFT monitor, so you'd expect the 8600 GTS to continue this pattern into the mid-range market and have 64 stream processors.

However, the 8600 GTS has only 32 stream processors and is therefore a little under-endowed, despite running at a respectable frequency of 1.45GHz. The GPU clock speed is also fast at 675MHz, and the 256MB of GDDR3 memory runs at a scintillating 1GHz (2GHz effective), although memory bandwidth is hobbled by a 128-bit wide bus. These compromises mean that the performance of the 8600 GTS is pretty disappointing, which is why its price has dropped by around £15 since it was launched last month. In S.T.A.L.K.E.R., we had to reduce the resolution to 1,024 x 768 to obtain a playable frame rate, which is disappointing for a brand-new mid-range card. The 8600 GTS is similarly unconvincing in Need for Speed: Carbon, with a few stuttery moments pulling the minimum frame rate below an acceptable level when playing at 1,280 x 1,024 with 2x AA and AF enabled. With the GPU already clocked to a very high level, the card refused to overclock any further than stock speeds. However, the peak power draw of our test PC with the 8600 GTS was just 199W, considerably less than any of ATi's similarly priced DirectX 9 cards.

The 8600 GT is smaller and less power-hungry than the 8600 GTS, and accordingly offers less performance. With fast cards from previous generations, such as the Radeon X1950 Pro, having dropped to around the same price as the 8600 GT, the card certainly has its work cut out. With a slower GPU speed of 540MHz, a stream processor frequency of 1.19GHz and 256MB of GDDR3 running at 700MHz (1.4GHz effective), the card returned pretty uninspiring results in our tests. F.E.A.R. ran well at 1,280 x 960 with 2x AA and 2x AF, although the average frame rate was 14fps slower than that of the 8600 GTS. Need for Speed: Carbon, on the other hand, would only run at 1,024 x 768, although the minimum frame rate of 27fps is borderline playable. Furthermore, the card simply wasn't powerful enough to play S.T.A.L.K.E.R. with all the detail settings maxed out. While the performance of the Radeon X1950 Pro isn't that much better in S.T.A.L.K.E.R., the Radeon's performance in F.E.A.R., and NFS: Carbon, in which it delivered playable frame rates at 1,680 x 1,050 and 1,280 x 1,024 respectively, means that the venerable ATi card effectively blows the new mid-range Nvidia card out of the water despite its energy efficient design - our test rig drew just 180W with it installed.

When compared with similarly priced cards from the previous generation, both the 8600 GT and 8600 GTS are underpowered. This makes us wonder how long it will be until Nvidia releases a new mid-range variant with 64 stream processors to combat the forthcoming Radeon HD 2400 and HD 2600.

Meanwhile, if you can afford to increase your budget then the 320MB 8800 GTS is a much better proposition due to its far greater performance; otherwise, the more sensible option would be to wait until there are more DirectX 10 cards from which to choose.

• Media PC components - 22nd August 2008
• PSUs - 14th July 2008
• Multi-GPU graphics - 20th June 2008
• CPU water cooling - 17th June 2008
• Hard disks - 20th March 2008
• Audio hardware - 29th February 2008
• Graphics cards - 24th January 2008

• Samsung SATA SSD 32GB - Hard disks / storage
• Spore - Games
• Zalman VF1000-LED - Other cooling hardware
• Arctic Cooling Accelero S1 Rev 2 - Other cooling hardware
• Antec Mini P180 - Cases
• Turok - Games
• ATI Radeon HD 4870 X2 - Graphics cards