Budget Video Card Comparison - November 2000

The ATI Radeon SDR

Of all the budget cards out there, ATI's Radeon SDR posses the finest line between itself and the more expensive Radeon DDR models. In fact, the core on the Radeon SDR is essentially identical to many Radeon DDR cores out there. Before we discuss how ATI chose to cut costs and differentiate between the upper end and lower end Radeons, let's see how powerful the Rage6C core is.

Operating at 166MHz in the Radeon SDR, the Rage6C core features two rendering pipelines, each capable of processing three texels per clock. This is unique, not only for value video cards but for performance cards as well. In the past, we have seen cards able to process two texels per pipe per clock. By including a third texel, the Rage6C is a perfect solution for tri-textured games. In situations where the video card is called upon to process three textures per pixel, the Rage6C is able to render the pixel in a single pass. In contrast, every other card at this price level is forced to use two passes to render the pixel, as each pipeline is only able to process two textures per pass.

The problem is that while the Rage6C core excels in tri-textured games, it takes a hit when a scene is only rendered in two textures. In this situation, the tables turn, with the Rage6C not able to take advantage of its extra texel per pipe. When rendering a dual textured scene, the third texel of the Rage6C's pipeline goes unused. Other dual texel cards, such as the aforementioned Voodoo4 4500 and the GeForce2 MX, are able to use both texels to render the scene.

As you can see, the Rage6C core would easily dominate in tri-textured games, as it is able to process 2 pixels per clock (using all three texels in each pipeline) while NVIDIA's GeForce2 MX, for example, would only be able to process 1 pixel per clock (using both texels in the first pipeline and only one texel in the second one). In principal, this is great, as more textures in game play equates to a higher level of detail. We run into a problem, however, when putting this theory into practice. Since the vast majority of games out there now are currently dual textured games, the Rage6C core is not able to fully use its 3 texel per pipe feature. In the future, this may change as games move to tri-textured rendering, but for now many Radeon owners are not getting the most from their card. The good news is that the Radeon SDR is able to match up perfectly to NVIDIA's GeForce2 MX when in dual textured games, as both the MX and the Radeon SDR are able to process a total of 2 dual textured pixels per clock cycle. The Voodoo4 4500 falls behind here, as it is able to process only one dual textured pixel per clock.

On top of the rendering pipelines, the Rage6C core also possess quite an impressive T&L engine, named the Charisma engine. The Charisma engine is able to perform all transform, lighting, and clipping calculations, thus freeing up some of the CPU power to perform other tasks. On paper, the Charisma engine is able to process 30 million triangles per second, however this number is hard to verify. The engine is also able to take advantage of quite a few DirectX 8 features, something no other card in this price range is able to do.

Combining the 166MHz clock speed and three texels per clock rating, we are able to see that the Rage6C core is able to process 1000 million texels per second, making it equivalent to a "gigatexel shader." There is quite a bit of power behind the core.