The GeForce 2 MX is a value card. It's designed for low cost and low performance. The GeForce 256 is a high-end card. They're targetted at different markets, much like the P3 and the Celeron, or the Athlon and the Duron. The MX was clocked down intentionally, has only a dual pixel pipeline, and only has SDR memory and is the only nVidia card which has TwinView. It's a card for the average user, not power-users or gamers. Still, for its price it's a pretty good card.