(http://www.trustedreviews.com/)Review After the arguably disappointing GeForce FX family of products, Nvidia has launched its latest graphics chip, which has been the subject of rumours from all corners of the world over the past few weeks. But now it's finally here and it's officially called the GeForce 6800. That's it, no fancy moniker in front of the numbers this time, just plain old 6800. But this time Nvidia has a product that will blow your socks off and no, I don't just mean a noisy fan this time around, I'm talking about the quality of the graphics and the outlandish performance, writes Lars-Göran Nilsson

Although I only had a chance to play with a reference card for a few hours, I can honestly say that this is the most impressive graphics card I have ever seen. We've been talking about cinematic graphics on the desktop for some time now, but the GeForce 6800 is the first graphics card to show signs of actually delivering on that promise. These are indeed very bold words and I don't say them lightly, even though it will be some time before we see actual games taking advantage of all the features of this new GPU. That said, there are titles such as Doom III and Half Life 2 around the corner, which should at least make you glad that you've got the latest graphics chip in your PC.

With a mind-boggling 222 million transistors onboard - that's just short of 80 per cent more than Intel's latest Prescott CPU - Nvidia claims that the GeForce 6800 Ultra will deliver up to eight times the pixel shading performance of its previous generation hardware. It should also deliver up to twice the vertex shader performance and close to twice the frame buffer bandwidth. On top of that it should also offer four times the shadow processing power and be up to four times more efficient at dealing with hidden surface removal. All this should have a massive impact on future games, with more advanced light and shadow effects than anything seen before.

Interestingly enough all of the new features aren't geared towards a faster, better looking, more advanced 3D environment, but rather towards video playback and recording. This might seem like an odd path for Nvidia to embark upon with a high-end graphics chipset such as the 6800, but with streaming media and high definition video becoming more popular by the day, it might not be as mad as it first looks. This, plus the fact that what's top of the range today, is tomorrow's mainstream product, makes a well rounded feature set all the more sensible.

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2D quality hasn't been forgotten either and the GeForce 6800 comes fitted out with dual integrated 400MHz RAMDACs offering sharp, vibrant performance all the way up to 2048 x 1536 at 85Hz.

The GeForce 6800 can also handle advanced MPEG 1, 2 and 4 video encoding and decoding, as well as WMV 9 decode acceleration. This should improve playback of DVD video as well as any current and upcoming streaming content. It should also offload your CPU during video editing and video rendering. I'm a bit uncertain if this makes the GeForce 6800 a viable alternative to a semi-pro video editing card, but this is something we will take a closer look at when we get a final production card.

Support for Microsoft's Video Mixer Render (VMR) enables playback of multiple video streams without loss of quality. With our US readership being HDTV enabled, native support is a must and nVidia offers this for playback up to 1920 x 1080i, which is pretty much as high as you can go. Even though HDTV broadcasts are some way off in the UK, with Blu-Ray and HD-DVD on the horizon, distributed HD media isn't too far off, so the ability to be able to playback HD content is a real bonus.

But let's take a closer look at some of the more interesting new 3D features. One of the most impressive features, that should have a massive impact in the way that computer controlled armies are created is the Vertex Frequency Stream Divider. This might all sound like marketing jargon to you and me, but there is some substance behind the name. What we're talking about is a way of programming variability into large groups of identical objects, to make them appear individual, even though the base model would be the same. Take for example a war game with a group of soldiers marching. Generated using traditional rendering technology they would be so synchronised that it would immediately look false and obviously computer generated. Apply the Vertex Frequency Stream Divider and suddenly you will have an army where each individual soldier can have his own unique attributes, subtle differences that make for a far more natural and much less mechanical look and feel. Not unlike the armies of orcs marching against Helm's Deep in The Lord of the Rings: The Two Towers.

This is something that so far has been extremely complicated to create in games due to the infinite amount of variations that could be applied, which would cause vast amounts of data to be processed for very little gain. Using Vertex Frequency Stream Dividers allows this to be done effortlessly and it can be applied in different ways depending on the type of game.

But this could not be done without support for Vertex Shader 3.0, which is meant to add near infinite-length Vertex programs and dynamic flow control that in turn removes the previous limits on the complexity and structure of shader programs. Breaking this down it means improved performance in games because routines can be looped and effects stacked on top of each other, rather than having to continually stop and start new routines for individual effects.

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Another new feature is Displacement Mapping, which is a simplified way of making complex objects look more realistic and adding more depth to graphics without creating the performance overhead previously associated with this. The easiest way to think of Displacement Mapping is as an advanced version of Environment Bump Mapping, but rather than adding bumps, the shape of the object is physically changed. An object with Displacement Mapping applied also reacts to the way light is applied to it with the textured surface of the object casting shadows in a way that Environment Bump Mapping would not.

The bottom line here is that Displacement Mapping will add a new level of geometric detail to objects making it easier for the game developers to add life like three-dimensional surface textures.

Next up is Pixel Shader 3.0, which is the one feature nVidia has been pushing hard. Along with similar Infinite-length Pixel Shaders and Dynamic flow control so fundamental to Vertex Shader 3.0, Pixel Shader 3.0 introduces Flexible Data Support and Multiple Render Targets. To fully understand all of these features you need a degree in 3D graphics, but I will try to touch on the core points of each of these new technologies.

Flexible Data Support gives programmers the flexibility to work in either 16- or 32-bit data precision depending on what they want to achieve and the resources available. Multiple Render Targets (MRT) is a variant of deferred shading, whereby pixel data is stored in multiple buffers until a scene's geometric detail has been calculated and rendered; at which point lighting data can be applied to the rendered scene. This saves multiple passes through the graphics pipeline, while also offering all the benefits of photo realistic lighting effects. The advantage of this is that the GPU has to do less work applying light and shadows to scenes for which it doesn't yet have all the information.

Nvidia is also introducing Rotated-Grid Anti-aliasing, which should vastly improve the quality of anti-aliased scenes. Traditional anti-aliasing using a two by two sub-pixel grid arrangement samples only two horizontal and two vertical values per pixel. By rotating the grid it can be positioned so that each sub-pixel samples four horizontal and vertical subpixel colour values instead. This is generally a far more accurate way of calculating colour values at the edges of polygons.

With complex lighting effects come complex shadows and though we give them little thought in the physical world, rendering them in games can cause a significant drop in performance. Although UltraShadow technology made its debut on the GeForceFX, the GeForce 6800 improves on this with UltraShadow 2 and a claimed potential fourfold increase in performance.

By removing the need for colour or texturing updates the GeForce 6800 generates stencilled shadow volumes at up to twice the standard pixel-processing rate. Nvidia also claims that game performance can be improved further with the use of a few specific UltraShadow 2 hardware calls.

Another acronym worth remembering is HPDR, or high-dynamic per-pixel radiance. Without throwing you a page of fancy equations, this allows a scene to contain the brightest of highlights and the deepest of shadows all displayed at once. Because standard 32-bit per-pixel frame buffers only gave 255 values to store the entire range of colour data, compromises often had to be made when scenes were rendered with a broad spectrum of lighting and colour intensities. HPDR technology broadens the programmer's palette and delivers greater data precision during shading, blending and filtering operations for both static and moving images.

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If by now you're as fed up as I am with all the techno babble and want to know how the GeForce 6800 Ultra performs, read on. Although this is only a preview, I managed to have a brief play with a pre-production board. There is one big drawback with the GeForce 6800 Ultra, if it can be called a drawback, which is the fact that there isn't a fast enough PC around to take full advantage of it. Even though we only tested the card in our somewhat outdated Pentium 4 2.4GHz reference system, it still managed to achieve some amazing numbers.

With a score of over 11,000 in 3DMark03, the GeForce 6800 is more than twice as fast as anything else we've tested. Looking at the performance numbers in the remaining benchmarks, the two that stand out are Halo and Tomb Raider: Angel of Darkness, both running at about twice the usual speed using the GeForce 6800 Ultra, compared to current crop of high-end graphics cards. This shows the benefit of upgrading to a GeForce 6800 Ultra today, even though current games can barely take advantage of even half of the features of the new GPU. With numbers like these you might be amazed to learn that the GeForce 6800 Ultra GPU is clocked at a mere 400MHz. It is backed up by blisteringly fast 550MHz GDDR3 memory, which has an effective speed of 1100MHz.

If you've saved up all your hard earned cash and planned to remortgage your house to get one of these new wonder cards, the good news is that as with recent top-end nVidia products, the GeForce 6800 Ultra will be launched at £399 inc VAT. And even if you don't have the fastest computer in the world, the GeForce 6800 Ultra will still do it justice as long as you're willing to play all your games at 1600 x 1200 resolution with 8x anti-aliasing and 8x anisotropic filtering. Nvidia sadly doesn't supply high-resolution monitors with the GeForce 6800 Ultra, even though it would be very handy if it did.

But what Nvidia should be supplying in the box is a discount voucher for a new power supply, as the GeForce 6800 Ultra needs two power lines to itself from the power supply. But worse than this is the fact that Nvidia recommends a minimum 480W power supply to make sure that the graphics card is supplied with enough juice. In return, you do get the most powerful graphics card on the market, which should convince enough users to fork out the extra money for a new power supply. Just don't expect to put one of these babies in small form factor box.

To sum it all up, the GeForce 6800 Ultra is the fastest and most impressive graphics card I have ever seen and I'm not easily impressed. On the down side, you do need a high-end PC and a small nuclear reactor, if you want to get the most out of it, but such is the lot of the early adopter. nVidia has snatched the performance crown back from ATi, but for how long, only time can tell. With ATI's next generation product just around the corner, this will be a very interesting summer for any hardcore gamers out there.

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