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"Current nVidia and AMD GPUs are just wide SIMD machines" That's not really true; you can kind of treat it that way, depending on the algorithm (eg, matrix mul
by fiatmoney 12y ago
"Current nVidia and AMD GPUs are just wide SIMD machines"
That's not really true; you can kind of treat it that way, depending on the algorithm (eg, matrix multiplication breaks down cleanly that way), but there are serious flexibility advantages in the "single-instruction-multiple-thread" model vs SIMD. For example, consider streaming large numbers of hash lookups - difficult to express clearly with a pure vector processing model.
- vardump 12y agoRight, I should have mentioned GPUs have a ton of hardware threads. Then again, they have to, GDDR5 memory access can take a microsecond. Try latency like that on a generic CPU, hyperthreading or not... So: GPUs are wide SIMD machines with a lot of hardware threads, massive branch and glacial memory latencies. When there's a branch or memory latency, HW simply switch thread. GPUs don't care about serial execution performance.