nVidia GeForce 6800 Ultra

They're here at last. After numerous rumours and leaks on the wires, and enough spin to make Alistair Campbell write a congratulatory memo, both ATi and nVidia have put their silicon where their mouths are. And let's be straight from the start: both companies have upped the ante to a truly astounding extent.
This shouldn't be too surprising, as the two reference samples reviewed here are each manufacturer's high-end offering for this year. They're built to last for the next 18 months, which in 3D card terms is several lifetimes.

nVidia GeForce 6800 Ultra
nVidia has decided to drop the FX moniker from its cards, one of the primary reasons being that it was 'unlucky' for them. The 6800 Ultra, formerly codenamed NV40, is a far bulkier beast due to a double-thickness heatsink and fan cooling system that will block the first PCI slot on your motherboard. It's still far lighter than the previous generation, though, despite packing a frankly absurd 220 millionÊtransistors.
The 6800 Ultra requires two Molex power connectors, and nVidia recommends that neither of these be in tandem with other components such as optical drives. It also requires a 450W power supply or above, so the majority of PCs will need to be upgraded. We'd cite this as a major flaw, but given the expense and quality of the card on offer here, an extra £20 on a new power supply seems a small price to pay.
And what an impressive specification it is. The GPU's clock speed may be lower than we'd expect, at 450MHz, but at least this gives plenty of space for the chip to be overclocked, be that by nVidia, the likes of Gainward or the owner. As with the ATi, there's 256MB of memory, but it's clocked slightly lower at 550MHz. It's also GDDR3 memory, originally developed by ATi, which runs on a specification designed for point-to-point graphics implementations. Its use in tandem with the enormous transistor count will likely explain the heat produced and therefore the need for such a large heatsink and fan combination.
While ATi merely put a digital video-in connector on the back of its reference design, nVidia has gone the whole hog and included an in-chip video processor. The main aim behind this is to take all the video processing away from the CPU, so it can dedicate its time to other tasks. We'll see why keeping the CPU as free as possible is so vital later. As well as basic video-processing features, editing support for MPEG-4 (including DivX), MPEG-2 and WMV9 (Windows Media Video 9) is included. This power will also allow for simultaneous playback of multiple video streams and time-shifting for PVR (personal video recording) purposes.
As with the ATi, DirectX 9b is supported, but nVidia has gone a stage further and provided support for Shader Model 3. This will be part of DirectX 9c and provides support for far longer shader programs that will allow for greater overall detail. While this makes no difference to the current crop of games, it's likely to have an impact on the next generation of titles, and is therefore very welcome. Finally, it also means dynamic branching is supported, while it isn't on the ATi chip. This means that the 6800 can skip complex shading instructions on irrelevant pixels, so it doesn't waste time shading darkness, for example.
Details about subsequent versions of the chip are few and far between, but nVidia has confirmed that a PCI Express version, codenamed NV45, will be available after summer. This will radically improve data transfer speeds, leading to even faster results.