Radeon X1900 XTX: Compromise and Its Consequences
There is a downside to each compromise, though. The realities of the PC world are different from those of the console realm. High resolutions and full-screen antialiasing are widespread here, and low quality of textures strikes the gamer’s eye immediately. Texturing speed is the crucial parameter in such modes and it directly depends on the number of texture-mapping units in the graphics processor. Moreover, even when a complex realistically-looking material is rendered by means of pixel shaders, such shaders have to contain a lot of texture lookups and thus put a considerable load on the graphics card’s TMUs and memory subsystem.
In other words, the quantity of TMUs is still a decisive factor in many cases, and the release of the G71 chip and the GeForce 7900 graphics card series confirmed that point. The senior member of the series GeForce 7900 GTX didn’t differ architecturally from the GeForce 7800 GTX 512, but had a higher core clock rate thanks to the transition to the 0.09-micron tech process: 650MHz against the predecessor’s 550MHz. This was enough to increase the efficiency of the GeForce 7900 GTX to the level of the Radeon X1900 XTX and even higher in some cases.
So, why was it so simple for Nvidia to restore the balance? Because game developers have to account for the huge amount of graphics cards currently in use that are not as good as the Radeon X1900 series at math1ematical calculations. So, if they used too many math1ematics-heavy shaders, they would leave quite a lot of users out of play, and this means lost profits. Besides that, the use of high resolutions and full-screen antialiasing brings about new requirements to the graphics subsystem as we’ve said above.
As a result, the combination of 24 TMUs with 24 PSUs (Pixel Shader Units) have proved to be almost as efficient as the combination of 16 TMUs with 48 PSUs. Yes, the GeForce 7900 GTX sometimes provides a smaller reserve of speed, i.e. has lower minimum performance, but in average performance it is at least no slower than the Radeon X1900 XTX and also has much better thermal and electrical characteristics.