Both ATI and NVIDIA have been pushing the PCI Express platforms hard, to the point where now it looks as though support for AGP is waning. However, initially ATI were at the forefront of the PCI Express transition, to the detriment of their AGP market. With the late arrival of their "Rialto" bridge chip ATI set about making one last high end native AGP graphics board with the Radeon X850 XT Platinum Edition.

The Radeon X850 XT Platinum Edition is powered by the R481 chip which is the AGP variant of the R480, which is in turn, the Autumn refresh for the R420/3 i.e. Radeon X800 XT series. Like the R480 and R420 before it, this AGP version is still built on 130nm low-k process, continuing ATI’s tradition of ramping clock speeds as production matures.

Although ATI's next generation X1000 series of graphics cards have been announced and released, it still looks as though there will be no high end AGP versions coming to market, even though the Rialto bridge could be employed, which currently still leaves the X850 XT Platinum Edition as ATI highest performance offering. With so many AGP systems still available we thought it would be useful to ascertain whether upgrading to ATI’s flagship AGP board introduced in late February, or something of a similar performance, is a good decision as opposed to changing to a PCI-Express system. This is especially relevant considering Intel AGP systems are pretty much at a dead-end in terms of CPU upgrade path.

In this article we’ll be examining whether a high-end Intel-based AGP system can make use of ATI’s top of the line board. This article will compare the XT PE to a Radeon 9800 PRO (R350); that although not the fairest of comparisons, it will demonstrate whether such an upgrade is worth it for Intel-based AGP systems.

The Graphics Chip

At this time the R481 is ATI’s top performing part for AGP systems, powering the X850 XT Platinum Edition, XT and PRO variants with the following specifications:

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Apart from the host interface type, there are no differences between the AGP and PCI Express X850 XT Platinum Edition, hence the same features are available, which are as follows:

    • 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
    • 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
    • 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
    • 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

For a more complete overview of the architecture behind the R480 graphics chip, you can find our R420 article (which shares its feature set with the R480 core) here.