Previous | Next --- Slide 47 of 74
Back to Lecture Thumbnails
jaez

It is mentioned here that the registers are scalar registers. Why are vector registers not used, given that the instructions are executed in a SIMD fashion?

abraoliv

@jaez If I understand correctly, the SIMD occurs across all the threads in the warp, not within any individual thread. Said differently, each thread operates on a scalar but if the same operations is being done across the threads in a warp, their scalars combine to make the vector for SIMD processing.

ghostcow

Right, this is my understanding as well. SIMD is executed across all threads in a given warp (similar to a "window size" in ILP); when n of these threads are running the same operation, that operation is executed using vector registers in one of the yellow execution units.