This is just out of curiosity. Let's, for example, take the 8800gt/9800gt and the HD 4830. They are both in the same performance league, yet the 8800gt has 112 shader units, and the 4830 has 640. I was wondering, they have to be different somehow... because less shader count on Nvidia cards matches higher shader count on ATI's. Are they architecturally different? If so, how?