I think you're asking about the distinction between SIMT (supported by GPUs/compute coprocessors), and SIMD. In SIMT, you want to issue a "bunch of the same wor

I think you're asking about the distinction between SIMT (supported by GPUs/compute coprocessors), and SIMD. In SIMT, you want to issue a "bunch of the same work on a crapload of pseudo-threads"—in the most hardware-efficient manner possible (vectorized). SIMD is different—it is all about the interactions between lanes of data. As a bit of a tautology: the vector unit in x86 parts is SIMD, because it was designed for SIMD workloads.