It’s not that GPUs are on a weird, parallel track trying to solve only the graphics problem—they actually got ahead of the more-general computing game by innovating in computer architecture. That’s very interesting, and if you’re a programmer, it’s the main reason you should be aware of these techniques and what’s going on. TD The interesting thing that’s been coming down the pike for the past several years is using these processors for computational purposes that don’t really have anything intrinsically to do with graphics. There were two competing directions driving all of this.

On the one side are the engineering workstations that SGI was building in the beginning that were running at

very high speeds, basically just drawing lots of polygons with simple shading—a very circumscribed sort of thing. Pulling the other way is the trend toward using a very general model to describe shading.

Now, those things pull in opposite directions. The performance of old-school GPUs really depended on the fact that we knew exactly what the algorithm was. All of the control junk that was in a normal CPU was pretty much irrelevant. KA It has been a smoother transition. People often say that programmability is a recent innovation in GPUs. Well, GPUs have been programmable for about the entire time that they’ve been built. With most SGI machines,