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We stand, unified
It's quite hard talking about a technology that will only work on an operating system and hardware that isn't available yet, however last week ATI decided it was worth a try.

Although ATI didn't go into huge detail about DirectX 10 nor their first GPU supporting it (R600), some nice overview on the upcoming "bleeding edge" was provided. The tastiest bit of information provided was unified shader architecture.

DirectX 10 introduces a new shader to sit in between the vertex and pixel shader. Called the geometry shader it allows triangles (the building blocks of 3D images) to be manipulated like objects. What this means is some very impressive 3D effects.

The reason why it's called "unified" is that all shaders, be it vertex, geometry or pixel can switch to become each other in a single clock cycle. That is to say, there will be no such thing as 12 vertex shaders and 12 pixel shaders "hard wired" in. The 12 pixel shaders can become 24 pixel shaders if there is no need for the vertex shaders.

ATI say this is a common occurrence in current games, where one set of shaders are being heavily utilized with the other being left dormant. Unsurprisingly this inefficiency is something that will be rectified in DirectX 10. Incidentally that Xbox 360 sitting next to your TV already takes advantage of this model (although what's inside of it isn't a DirectX 10 compatible part).

Click to enlarge The part of the chip that decides whether a shader should be vertex, geometry or pixel is the thread arbiter. ATI states that this piece of technology brings almost 100% efficiency in shader usage. When asked how big a part of the GPU the arbiter was, ATI declined to give figures but stated it was "significant".

ATI assured us that there is absolutely no performance difference between an "unified shader" set to be a vertex shader and a dedicated vertex shader.

Other changes include the removal of 'partial precision'. All calculations will be done in 32-bit and anything less will fail Microsoft's WHQL certification.

Another interesting aspect of DirectX 10, or rather it's certification is that all vendors (NVIDIA, ATI, Intel, S3 etc) can introduce features on top of what's required. ATI have already stated they will be doing this. This begs the question whether games will be developed to take advantage of extra features only available on a single vendor's GPU. Of course this is nothing terribly new but with all the talk of unification, it does seem like a small backtrack.

The games of tomorrow will bring further detail in worlds, with better physics and character animation thanks to DirectX 10 and it's ability to reduce overhead from the GPU.

DirectX 10, available only for the upcoming Microsoft Vista operating system is something of a technology in the shadows. As it will only work with Windows Vista and nothing else, games that utilize DirectX 10 will mean you have to upgrade your machine to Microsoft's latest operating system. What this means is that games publishers may only allow developers to pick up this technology when Windows Vista adaptation hits a critical mass.

There's no doubt from a developer's point of view DirectX 10 offers extra tools to do more neat things, the problem is being restricted to just one operating system may mean we have to wait a very long time before we see the advantages on a wide array of titles.