There are 1600 Alus, but they are grouped in vliws of 5 elements, which are grouped in simd groups of 16 vliws. So there are 20 front ends, and reading a single

There are 1600 Alus, but they are grouped in vliws of 5 elements, which are grouped in simd groups of 16 vliws. So there are 20 front ends, and reading a single bundle in one of them will instantly make 80 alus execute an instruction. The barrel is essentially used to extend the vector registers from 16-elem to 64-elem, and a 64 "thread" wavefront, consisting of 5 VLIW'd instructions is essentially the smallest amount of work that R700 can do.