3 ms·
It feels like chipmakers never learned to "Make it work, make it right, make it fast", in that order. But then, hindsight is 20/20. How much slower would proce
by sholladay 3y ago
It feels like chipmakers never learned to "Make it work, make it right, make it fast", in that order. But then, hindsight is 20/20.
How much slower would processors be if they got rid of all complex / risky optimizations? How much performance could we gain back with more expensive components, more integration (e.g. SoCs), and other approaches that are unlikely to lead to security problems?
- weebull 3y agoHow much slower? - we diable speculative execution, so every conditional branch goes for 1 cycle to the pipeline depth (5, 10, 20 cycles) to evaluate. Probably a 2x to 3x hit on performance. - we disable prefetching, so every cache miss now has the full memory latency delay to fill a cache line. 1.2 to 1.3x hit??? - We disable SIMD as per this issue. 4x-8x hit on those parts of the code that usebit. - If we need to go as far as disabling caching you can now only run instructions at the speed of main memory. 100x hit. CPUs would only be faster than their 1970s ancestors because the clock speed was now 5GHz and not 1 MGHz.