The Graphics Chip

First lets take a look at the chip details of the R420 to see how its implemented.


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ATI's recent silicon execution plan has been to experiment with most advanced processes on their smaller, mid-range chips to minimise the risk of implementation, and then take the knowledge learned from that and apply it to their high end. It was for this reason that R300 was only introduced on 150nm, as they had prior knowledge of 150nm processes with R200; RV350 allowed ATI to get to grips with 130nm and subsequently RV360 with 130nm low- k. The understanding of potential pitfalls of 130nm low- k from RV360's engineering could then be applied to R420 as their high end introduction. This execution plan appears to have served them well as they state they are to be shipping on the first silicon revision, however we understand that there was some hold-up due to the initial batch of chips back from the fab having some process issues that were promptly rectified by TSMC.

The following is a list of the significant features that the R420 chip makes available to end users:

  • SMARTSHADER HD
    • Support of DirectX9 Programmable Vertex and Pixel Shaders
    • VS2.0 Vertex Shader functionality
      • Up to 65,280 instructions including loops and subroutines.
      • Single Cycle Trigonometric Operations (SIN & COS)
    • DirextX9 Extended Pixel Shaders
      • Up to 1,536 instructions and 16 textures per rendering pass
      • 2nd Generations F-Buffer support for unlimited Shader instruction lengths
      • 32 temporary and constant registers
      • Facing register for two-sided lighting
      • Multiple render target support
      • Shadow volume rendering acceleration
      • 128-bit, 64-bit & 32-bit per pixel floating point colour formats
  • SMOOTHVISION HD
    • 3Dc Normal Map Compression
      • High quality 4:1 Normal Map Compression
      • Works with any two-channel data format
    • 2x/4x/6x Multi-Sampling full scene Anti-Aliasing modes, adaptive algorithm with programmable sample patterns and colour buffer compression
    • Temporal Anti-Aliasing
    • Lossless Color Compression (up to 6:1)at all resolutions, including widescreen HDTV resolutions
    • 2x/4x/8x/16x anisotropic filtering modes
  • HYPER Z HD
    • 3-level Hierarchical Z-Buffer with early Z test
    • Lossless Z-Buffer compression (up to 48:1)
    • Fast Z-Buffer Clear
    • Z Cache Optimisations for shadow rendering
    • Optimized for performance at high display resolutions, including widescreen HDTV resolutions
  • VIDEOSHADER HD
    • Seamless integration of pixel shaders with video FULLSTREAM video de-blocking technology
    • Noise removal filtering for captured video
    • MPEG-2 decoding with motion compensation, iDCT and colour space conversion
    • All-format DTV/HDTV decoding
    • YPrPb component output
    • Adaptive de-interlacing and frame rate conversion

If you think these features look scarily similar to R300's capabilities with an "HD" (High Definition) stuck on the end, you'd be correct, they are. R420 is an extension on R300's hardware capabilities, only introducing a couple of significantly different elements, but mostly taking the current design and extending / refining it. We'll take a closer look at some of the changes later on in this article.