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VLIW is just a way of achieving instruction level parallelism. That 9:1 speed-up is vs a single issue, in-order core, which PCs haven't used since the mid-90s.
by mechagodzilla 11y ago
VLIW is just a way of achieving instruction level parallelism. That 9:1 speed-up is vs a single issue, in-order core, which PCs haven't used since the mid-90s. Modern superscalar processors can not only handle multiple instructions in parallel, but extensions like AVX allow very wide instructions for embarrassingly parallel things like matrix operations. We've probably achieved 95% of the theoretical speedup from amazing VLIW.
- graycat 11y agoSo, just when did we get that 8:1 or 9:1 speedup without having the processor clocks run faster. IBM was doing speculative execution, branch prediction, out of order execution, and vector instructions also in the 1990s. There were careful instruction level traces of the advantages and speedups. Of course, vector instructions are for special purpose code, e.g., the ubiquitous inner products in linear algebra, probability, and digital filtering, but 9:1 was on general purpose code. IIRC, the instruction traces didn't show 9:1 or anywhere near that.