Been looking at ATI streams and Nvidia shaders and it look like 10 ati stream shaders = 1 of nvidia's. It is sort of like comparing apples to oranges they both do the job not nothing alike. Or something known as patents that made ATI/AMD make shaders totally different. Compare my card has 64 shaders and the ATI = card 4770 has 640. It also looks like 40 streams you get getting dropped are used for maybe error correction in the ATI cards. Not 100% sure without digging deep into how a ATI/AMD shader stream does its math.