LOSTCIRCUITS

AGP X8

After the introduction of the SIS Xabre cards, the ATI Radeon 9xxx series is the second to feature an AGP 8X interface to ensure enough bandwidth from the system to the graphics card. At low resolution, the increase from 1 GB/sec (AGP 4X) to 2 GB/sec will not result in any performance increase, however, with increasing texture size and resolution we can expect a sizeable delta, at least in future games.

R300 Chip Architecture Overview

Four Vertex Decoders

   

Four programmable vertex shaders double the amount of vertices that can be processed from the nVidia GeForce4. On the right is a closeup of the individual subunits of each vertex shader

Like Matrox's Parhelia, the R300 features four programmable vertex shader pipelines which is twice the number of pipelines found in the GeForce4. Each Vertex Shader pipeline can simultaneously process one vector and one scalar operation. Vectors are typically composed of three scalars (x,y,z) plus color. Keep in mind that any vertex shader can only use its power if there are enough triangles that it can actually use. This appears no issue with the R300 since its triangle setup engine is capable of setting up 1 triangle per clock cycle. At 300 MHz clock speed, this results in a blazing 300 million triangles per second, enough even to satisfy a quad vertex pipeline and fill the screen.

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