p.o.d. was the poster child for the
MMX instruction set. It was a computer game with a racing theme, filled with complex textures and semi-sophisticated
game physics. You could create your own custom car, setting things such as acceleration, traction, top speed, etc. which made it better than many of the previous car games.
Only problem (for me, ymmv) was the graphics were so complicated that the cars tended to get lost in the environment, and the physics were at such a level where several cars were all but unusable if it came to turning (due to acceleration and turning stiffness).
The storyline went something like this: you're a convict on a prison planet, and these tournaments are held as entertainment for the populace. You are vying for a chance to regain your freedom by winning the race in the allotted time. Your opponents do not need to survive the race.
It was on just about every demo machine I saw several years back, has seemed to have faded into the mists of time.