X-bit labs

ATI RADEON X800: R420 Totally Exposed (page 8)

Category: Video

by Tim Tscheblockov , Alexey Stepin , Anton Shilov

[ 05/04/2004 | 06:42 AM ]

Vertex Pipelines, Vertex Shaders

First of all, I would like to say that RADEON X800 acquired more vertex processors: their number has been increased up to 6 (the previous generation high-end graphics chips from ATI featured only 4 vertex processors). If we also add here the slight increase in the clock frequencies, we will be able to immediately evaluate the minimal geometrical performance boost we will get when shifting to RADEON X800 solution.

The geometric part of RADEON X800 consists of 6 processors and a set of non-programmable functional units responsible for projecting vertexes processed by the pixel processors onto the screen surface, setting initial parameters for HyprZ and splitting the vertex triangles into tiles, setting the initial parameters for pixel processors, creating queues of 4-pixel blocks, etc.

Each of the vertex processors of the new RADEON X800 features two ALUs, which can perform commands in parallel: these are the vector and scalar ALUs. The calculations are done in 32bit floating point format.

RADEON X800 vertex processors do not support dynamic branching and loops in vertex shaders, just like the pixel processors. Together with the absence of texture sampling units this fact eliminates all the hopes to see RADEON X800 support vertex shader version 3.0 on the hardware level.

So, as for the vertex processors, RADEON X800 also boasts a few improvements compared with the previous generation architecture. They changed the functionality of the vertex processors, as well as the overall geometrical pertformance of the RADEON X800.

A little later in our today’s review we will be able to evaluate the vertex shader processing speed as well as the geometrical performance of the RADEON X800 XT Platinum Edition and RADEON X800 PRO solutions in the synthetic benchmarks. And now let’s say a few words about HyperZ HD, a new technology aimed at increasing the efficiency of the graphics processor resources.