Like the G80 core, the R600 core from ATI sports a unified architecture. We wrote about this in our review of the 8800GTX, so to save ourselves from writing it again here it is, copy-pasted:

“A unified shader is one that is capable of executing both vertex and pixel shading instructions. Whereas in the past the number of pixel shaders and vertex shaders were carefully balanced and differed from card to card, unified shaders allow manufacturers to use more where more are needed. Imagine having a set of 10 dudes on either side of a wall. All of a sudden, a whole bunch of work is dumped on one side of the wall that will take the 10 dudes 2 hours to complete. Meanwhile, the other 10 dudes are just chilling on the other side of the wall, not only because there is a wall in the way, but because they speak a different language than the other 10 dudes so they wouldn’t be able to do the work that they are doing in the first place. Now imagine all 20 dudes are bunched together and all speak a singular hybrid language. That same work load is dumped on the 20 dudes and they are able to knock it out in 1 hour.”

Epic, we know. Although the unified shader concept is similar between the two cores, the way they go about presenting this functionality is a bit different. Whereas the G80 has 128 aptly-named “Unified Shaders”, the R600 has 320 “Stream Processors”. Clearly 320 is a bigger number than 128, but as we know in the hardware world, bigger numbers don’t always mean something is better. The fact of the matter is that Stream Processors are different than Unified Shaders. ATI’s Stream Processors are an integral part of the Superscalar architechture implemented on the R600. There are indeed 320 physical processors on the R600 CPU, but some of them are standard ALU’s and some of them are special-function ALU’s. NVIDIA has stated that they do not agree with how ATI counts their processors, proclaiming that they only count standard ALU’s on their G80 core. In any case, the approach to counting and placing these processors on the core differ between the two companies, so unfortunately nobody in their right mind will ever be able to compare these two things directly. That’s OK with us though, because we only really care about how the card performs.



Finally we have another card that supports DirectX10. However, one of our earliest fears about DX10 seems to be coming true already: by the time games are actually ready to be enjoyed in full DX10, the cards that were first to launch touting support for the new API will be vastly inadequate. To date there are something like four noteworthy titles that support any shred of DirectX10, and all four of them accommodate the API via a patch, meaning they are DX9 games ported over. Supreme Commander, Company of Heroes, Call of Juarez, and Lost Planet are all games that support DX10 in one way or another. After having anticipated the release of this update for quite some time now, our feelings about DirectX 10 have become pretty strong – strong enough to warrant us giving it its own section near the end of this article (don’t just hop to it though, there’s plenty of other interesting stuff along the way! We promise!). Of course alone with DX10 comes support for Shader Model 4.0, the natural progression from Shader Model 3.0 that was first showcased in NVIDIA’s 6 series. Talking about any of the other specs of this card would be a little bit premature even after the R600 core was released in its first incarnation over a month ago. Drivers for the product still seem to lack support for some of the features that the card supposedly has, and all of the other features besides the AA+HDR (which works) are nothing particularly ground-breaking.