ATI's 512-bit Ring Bus & R520 Product Naming

The 90nm R520 components will come in three versions, all inside the X1800 Radeon naming convention. The marketing information received at Anandtech claims that the GPU uses an "ultra-threaded quad-core 3D architecture" and a "512-bit ring bus" memory controller. Most of that will be marketing language but here are the details:

The "ultra-threaded quad-core" design just describes any standard GPU. X800XL/XT would also qualify as ultra-threaded and quad-core, as would the 6800GT/Ultra. They have a core split up into groups of "quads" - four pixel pipelines that can be deactivated as a group in case one of them is faulty. General consensus from the documentation is that there are once again four quads, so expect to see 16 pipes on this card. There are some "confirmations" of 24pp and 32pp, but the roadmaps clearly say four cores/quads (at least to begin with) due to production yield. All signs indicate that a future generation, R580, will use six cores instead.

The 512-bit internal ring bus actually excites the most; Cell's Elemental Interface Bus (EIB) uses a 16-byte wide quad ring bus, capable of transferring 16-bytes per cycle to the various SPEs. R520's ring bus would actually be four times wider than the bus found on Cell; though this implementation is in R520's memory controller rather than the PPE-to-SPE interface. With all the hype for R520 so far, everyone is banking on the memory controller to put X1800 ahead of G70. However, there is once again some hype occurring. The memory subsystem is still connected by a more typical 256-bit memory bus, and the 512-bit ring bus is something else. We'll have to wait for actual cards and benchmarks before we can really discover how the card performs.

Other interesting technologies on R520 include Shader Model 3.0 (and thus HDR), Adaptive anti-aliasing, and up to 512MB of GDDR3 memory. Sources indicate that only the Crossfire versions of X1800 will support 512MB initially, but this may change further downstream. Radeon X1800, X1600 will also feature ATI's new Avivo technology. There was also indiciation in the roadmap that this generation of ATI cards will fully support Windows Vista, with beta drivers already available. Rumour has it that ATI will launch at least one product on October 5th, 2005. Mid-range card and entry-level card information is available at Anandtech.