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Evesham's Solar 8600GTS PC is the first system to use these promising new cards - read our full review here.

With previous mid-range GeForce GPUs garnering huge praise for offering great performance at very reasonable prices, the new chip has much to live up to. At launch there are two flavours of GeForce 8600 - the GTS and the GT - with the former being the faster chip.

The architecture

They're architecturally identical, both containing 289 million 80nm transistors, most of which are from the 32 stream processors. These have a unified shader architecture to allow them to process any kind of game data, from the usual vertex and pixel to the new geometry shaders and even physics calculations. Both chips also have 8 Render Output Processors, allowing them to send 8 finished pixels to the frame buffer per clock.

This frame buffer is set to be 256MB on both versions (though expect variations such as 512MB or 128MB), with a 128-bit interface to help data flow to and from this graphics memory. That's enough for most modern games, although texture-heavy DirectX 10 games will likely push this to the limit.

The products are differentiated by their clock speeds, with the GTS clocked much higher than the GT. The 32 stream processors of the GTS run at a breakneck 1.45GHz, which is even faster than those running in the top-end 8800 GTX. The 8600 sees a slight improvement to these stream processors too, with the ability to address twice as many (eight) texture locations per clock as an 8800 stream processor.

Around this super-quick shader core are the set-up engines and thread dispatch units to feed it, and those 8 ROPs to deal with the results. This collection of sub-units (strangely referred to by Nvidia as the GPU 'core') run at a stellar 675MHz, again faster than the equivalent parts of an 8800GTX. And to match those super-high clock speeds in the 8600 GTS GPU, it'll ship with RAM running at 1GHz, a feat matched by only the top-end ATi Radeon X1950 XTX.

The 8600 GT has more modest clocks, with its 32 stream processors running at 1.19GHz and its 'core' at 540MHz, while its RAM runs at a more modest 700MHz. And while HDCP is guaranteed with the 8600 GTS, it's a card-maker option with the GT so read the specifications carefully.

Game performance

But enough of the theory, how do the two cards perform? The simple answer is very well: at our Standard settings (see below for details) only the toughest of games and settings brought either the GTS or the GT to an unplayable frame rate.

The GTS raced to a score of 53fps in Far Cry, 36fps in Call of Duty 2 and a fairly impressive 24fps in Elder Scrolls IV: Oblivion. Dropping the antialiasing and anisotropic filtering

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(AA and AF) from the latter two tests boosted the score to 43fps and 53fps respectively; pretty high scores for even top-end DirectX 9 graphics cards.

The GT predictably fared less well, but still managed a healthy 42fps in Far Cry, although Call of Duty 2 dropped to 29fps and Oblivion to 21fps. Again, losing the AA and AF brought a huge performance gain, with the latter two games becoming playable with scores of 35fps and a mighty 44fps respectively. At 1,280 x 1,024 the 8600 GT has enough clout to play even the toughest of games, but whether this will translate into DirectX 10 performance is anyone's guess - there's still no sign of any games being released in the next few months.

Curious to see how the 8600 GTS compares to the higher-end 8800 GTS, we ramped up the testing to our High settings (see below). Again Far Cry produced a playable frame rate of 36fps, but Call of Duty 2 proved more troublesome, as our test requires 512MB of local graphics memory thanks to the Extra texture settings we use. The score of 18fps is therefore unrepresentative of the GPU.

Using the 256MB-friendly High textures and dropping the AA and AF produced a barely tolerable 32fps. Oblivion is playable at 1,600 x 1,200 with no AA and AF though, racing along at 42fps.

This can't compare to even the GeForce 8800 GTS 320MB card, though, which scored 57fps in Oblivion with 4x AA and 8x AF in the same test rig. The 8800 clearly remains the most future-proof investment.



Far Cry (standard settings)

Call of Duty 2 (standard settings, no AA or AF)

Conclusions

All of this is pretty good news for Nvidia fans - as are the projected pricings. At $149 we expect the 8600 GT to cost around £80-100 over here, and considering it will blitz all your games at 1,280 x 1,024 without any image quality sacrifices, it's looking an attractive buy.

The 8600 GTS meanwhile is projected to cost $199 to $229, which should translate to £110-130. Again, considering the bags of performance on offer that's an incredible price.

Cards are already available from online retailers and there's even the extra promise of 100% GPU-based High Definition decoding. Alas we haven't had time to fully test this yet, but we'll update you as soon as we have the results.

SETTINGS
Standard settings
Far Cry - 1,280 x 1024, no AA or AF, maximum detail settings, HDR
Call of Duty 2 - 1,280 x 1,024, 4xAA, 8xAF, High texture settings
Elder Scrolls IV: Oblivion - 1,280 x 1,024, 4xAA, 8xAF, maximum detail settings

High settings
Far Cry - 1,600 x 1,200, no AA, 8xAF, maximum detail settings, HDR
Call of Duty 2 - 1,600 x 1,200, 4xAA, 8xAF, Extra texture settings
Elder Scrolls IV: Oblivion - 1,600 x 1,200, 4xAA, 8xAF, maximum detail settings

TEST KIT
2.66GHz Intel Core 2 Duo E6700; Intel 975XBX motherboard; 1GB Corsair 800MHz RAM; 36GB Western Digital Raptor