X-bit labs

The Fast and Furious: ATI Radeon X1900 XTX Review (page 4)

Category: Video

by Anton Shilov , Alexey Stepin

[ 01/24/2006 | 08:28 PM ]

Radeon X1900: Architected for the Future

One of the main achievements for ATI in the case of the Radeon X1000 architecture was easy scalability: adding more pixel shader processors is now much easier for ATI and does not require designing a new GPU from the scratch, which simplifies adding performance to the part greatly.

Having developed an architecture that swaps traditional pixel pipeline for a set of blocks that are controlled by a special ultra-threading dispatch processor, ATI gave us a glimpse onto the future of graphics processors as well as its abilities to boost performance of the Radeon X1000 chips.

The Radeon X1900 graphics chip, also known under code-name R580, is a reincarnation of the Radeon X1800 visual processing unit (VPU) with 48 pixel shader processors, enlarged by 50% hierarchical Z-buffer (HyperZ buffer), higher amount of general purpose register arrays as well as Fetch4 feature designed to accelerate lookup of textures consisting of one component by the factor of four (when looking up different types of textures with single-component values [such as shadow maps], Fetch4 allows four values from adjacent addresses to be sampled simultaneously, which effectively increases the texture sampling rate by a factor of 4).

 
Radeon X1800 (left) and Radeon X1900 (right) internal architecture in brief. Click to enlarge

Pure pixel shader power of the R580 increased 3 times - or by 200% - over the R520, whereas the transistor count increased by about 60 million – or by approximately 20% in total. It remains to be seen whether actual gaming performance will increase by 20%, but we have to keep in mind that the Radeon X1900 was architected for future games and immediate benefit may be lower than long-term benefit.

Let’s have a look at the specifications of the Radeon X1900: