4 ms·
It's not free though. If you can actually remove most of the power/area hungry ooo scheduling logic for only 10% less performance on real world workload, you ca
by obl 8y ago
It's not free though. If you can actually remove most of the power/area hungry ooo scheduling logic for only 10% less performance on real world workload, you can pack a lot more cores or a bigger GPU on the same chip without blowing up TDP or die size.
Sure, some use case will always require the highest single thread perf at all cost but that's less and less true these days.
- thesz 8y agoThe speculation must be done with content-addressable memory, because you must commit or rollback register mapping after speculative execution have succeed or failed. The dynamism, on the other hand, is a way to issue (possibly) out of order commands when they are ready to be executed (their inputs are ready and no write conflicts detected). For this you need a scoreboard (which is also needed for speculative execution). Scoreboards are for registers (which one is ready, etc) and for commands (which one is eligible for execution). As you can easily assume, these scoreboards are bit vectors, not some interesting thing that maps 80 internal registers to 16 externally accessible register indices. The scoreboarding in CPUs have long history. They were used in Burroughs' CPUs long ago. They were used in early Alpha AXP designs (first one or two, I guess). They are very easy to implement - yours truly is guilty in this, having done that in month and he is not even a hardware designer.