Verdict: DirectX10 for less than £100
One of the ways in which Nvidia has thoroughly banished all memories of the disastrous GeForce FX series - apart from the cloves of garlic seen hanging from the windows at its Santa Clara headquarters - has been by producing several generations of storming mid-range GPUs. The GeForce 6600 and 7600, particularly in their premium GT incarnations, were quick enough to power the latest games at full detail on mid-range monitors, and their prices didn't make your blood run cold.
The GeForce 8600-series is Nvidia's newest family of mid-range GPUs but, bewilderingly, the GT isn't the fastest version of the chip - that honour goes to the GTS.
This odd little switch with the names isn't the only thing that's confusing about the GeForce 8600 GT; look under its skin, and matters become thoroughly weird. Not that all this weirdness is bad. Like the GTS, it's a fully DirectX 10-compatible GPU, with a unified architecture, so the traditional approach of using discrete pixel and vertex pipelines is dead and buried. Like the 8800-series, the 8600 GTS and GT have banks of stream processors, general-purpose arithmetic logic units that can cope with pixel and vertex shader code, as well as DirectX 10's new geometry shader instructions.
The GeForce 8800 GTX has 128 stream processors, while the 8800 GTS has 96. If you guessed the GeForce 8600 would have 64, or even 48, then you'd be wrong - like the 8600 GTS, the GT has only 32 stream processors. Nvidia claims that it's tweaked the GPU design to improve 'per-clock shader performance', although it won't provide any details about this. The number of ROPs has also dropped to eight in both the 8600 GTS and GT. In real terms, this means a massive reduction in pixel fill rate compared with the 8800-series. However, as the emphasis in modern games is on shader performance, this should only hurt the 8600 GT at high resolutions, which are way out of its league anyway.
Aside from sharing the unified architecture of the GeForce 8800-series, both 8600 GPUs benefit from the same increased image quality, thanks to Nvidia's Lumenex engine. This means that unlike the GeForce 7-series, the new GPUs support anti-aliasing with HDR lighting. The 8600s can also provide anti-aliasing up to 16x, and Nvidia has tweaked the texture processors in the GPU in order to assist with this, essentially doubling the number of textures address units per block of 16 stream processors to eight (providing 16 in total). The 8800-series has four texture address units per block of 16 stream processors, which obviously provides more units overall (24 in the 8800 GTS, for example). By default, the GT is clocked at 540MHz, compared to 675MHz for the GTS. The stream processors of the GT run at1.19GHz, while the processors in the GTS run at 1.45GHz.
There's some method to these tweaks, but the memory arrangement of the 8600s seems to carry a hint of madness; both the GeForce 8600 GTS and GT only have 128-bit memory interfaces, compared with the 256-bit interfaces toted by AMD's current mid-range Radeon X1900 and X1950s, and the whopping 384-bit interface of the GeForce 8800 GTX. Normally, a 128-bit memory interface would equate to dire memory bandwidth but Nvidia has countered this by outfitting both the 8600 GTS and GT with fast memory. The GT has 256MB of memory running at 700MHz (1.4GHz effective), giving it 22.4GB/sec of bandwidth, exactly the same as that of the GeForce 7600 GT.
Both 8600s sport PureVideo HD, which means they can accelerate H.264 video, but only the GTS natively supports HDCP. In the case of the GT, weirdly, this matter is down to the individual manufacturers, which will no doubt be thoroughly confusing for consumers.
The two cards differ physically as well; both are currently 16x PCI-E, but only the GTS requires an additional power plug, which doesn't bode well for thrifty overclockers hoping to simply bump the clock speeds of the GT up to GTS levels.
MSI was the first company to supply us with a GeForce 8600 GT, and opted to send us an overclocked model, the NX8600GT-T2D256E-OC. The GPU clock has been boosted by 40MHz to 580MHz, and the memory by 100MHz to 800MHz (1.6GHz effective). MSI has also chosen to use its own chunky cooler; annoyingly, though, this continues the disappointing yet long-lived tradition for mid-range Nvidia GPUs: it's noisy and annoying, much like a Westlife Greatest Hits CD. It's also louder and more irritating than the Nvidia reference HSF.
Performance
Performance-wise, the MSI wasn't stunning, especially when we pushed the resolution above 1,280 x 1,024. F.E.A.R. was pleasantly smooth and playable at 1,280 x 960, but its average frame rate is only 6fps faster than that of a reference GeForce 7600 GT. Worryingly for Nvidia, the similarly priced Radeon X1900GT is much faster, averaging 67fps at the same settings in the same test rig - 17fps faster than the MSI.
In Need for Speed: Carbon, 'Need for Speed' turns out to be a depressingly accurate statement for the MSI - it struggles to make the game smooth enough to be playable even at 1,024 x 768. Carbon is hardly an era-defining game, but it's galling that a brand-new GPU can't cope with it.
Prey's portals proved to be very tricky for the 8600 GT; while the MSI averaged 41fps at 1,280 x 1,024 with 2x AA and 2x AF, the minimum frame rate didn't feel high enough, and we'd opt to turn off AA and AF to keep the game smooth. The MSI didn't put any significant distance between itself and the GeForce 7600 GT, with an average frame rate just 3fps higher than that of the older card. Again, the Radeon X1900GT was quicker, averaging 50fps compared to the MSI's 41fps.
Indoors in Oblivion, the MSI averaged a strong 43fps at 1,280 x 1,024, 10fps slower than the BFG 8600 GTS. Outdoors, the average frame rate plunged to 26fps. This is nearly identical to the frame rate of the BFG and the Radeon, showing that none of these cards really has the power to handle Oblivion's outdoor environments.
Our final test was Company of Heroes, and the MSI averaged 35fps at 1,280 x 1,024 with AA on, which was enough to make the game playable, but some way behind the BFG's average of 42fps.
Despite the fact that MSI ships the card overclocked, we tried tweaking the card further, using ATITool. We managed to achieve a pretty respectable overclock, pushing the GPU to 670MHz, and the memory to 820MHz (1.62GHz effective). Nvidia clearly sees good results from faster clock speeds, as the GTS is a faster-clocked GT, so it wasn't surprising that our overclock gave the scores in F.E.A.R. a real shot in the arm - at 1,280 x 960, the average leapt from 50fps to 55fps.
Concclusion
It's great to see MSI shipping cards that are pre-overclocked and have a different cooler. Although the cooler is far too noisy for its own good, it allows for overclocking, so it's obviously effective at shifting heat from the GPU.
Costing less than £100, the MSI is also cheaper than we expected, and really does promise DirectX 10 for the masses. The only problem is that its performance isn't as good as we'd hoped it would be. It's slower than the similarly priced X1900GT, and the X1950Pro, for just £20 more, offers far more performance. The MSI isn't the best buy in terms of speed and, while it wins on features, since it's compatible with DirectX 10, as there are no DX10 games at the moment, there's no way to know how well it will run these next-gen titles.
