A GeForce4 with 30M Transistors?

Let's have a quick look at the high-level specs of the XP4 before we get much further:

  • 0.13-micron GPU clocked at 250 - 300MHz
  • 30 million transistors
  • 4 pixel rendering pipelines, 2 texture units per pipeline
  • 2 programmable vect4 vertex shader pipelines
  • 64/128-bit DDR memory bus
  • up to 256MB of memory on board, clocked at 250 - 350MHz (500 - 700MHz DDR)
  • Tile-based rasterization engine
  • AGP 4X Support
  • Full DX8.1 Pixel and Vertex Shader Support with a base level of DirectX 9 support

As you can see from the above spec-list, the XP4 is a 0.13-micron chip, fabbed at UMC and it is only composed of 30 million transistors. To put things in perspective, the GeForce4 is a 63M transistor chip and the ATI Radeon 9700 is made of close to 110M transistors; the XP4 has a transistor count equal to that of the original Radeon and just slightly more than the GeForce2 GTS. Although the XP4 is built on a smaller process, that does nothing to reduce transistor count, so the transistor savings must come from somewhere else. The low transistor count is the key to Trident's ability to price XP4 graphics cards at under $100, but how do they achieve it?

Just looking at the number of vertex shaders and pixel rendering pipelines, you can tell that the GPU is very much like a GeForce4; they both have two vertex shaders units and four rendering pipes with two texture units per pipe. These two areas of the GPU take up the vast majority of the space (and thus transistor count) on a GPU, so it would make sense if Trident managed to decrease the XP4's transistor count by tinkering around here. It's unfortunately this area that Trident is the least forthcoming with information because of their desire to protect their IP that went into the production of the XP4, which is understandable but it limits what we can explain to you all.

Index Truly Four Rendering Pipelines?

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