3 ms·
To be clear, are you trying to point out that their charts look like in-order modelling on an out-of-order CPU? Sequential dependencies, especially those exist
by knappador 13y ago
To be clear, are you trying to point out that their charts look like in-order modelling on an out-of-order CPU?
Sequential dependencies, especially those existing in looping calculations, turn out-of-order execution into in-order execution. There's no way to re-order the execution beyond some degree of dependency. I don't know what the word for it is, but an engineer will sooner compress a movie to one bit than enable re-ordering certain kinds of sequential dependencies. There's nothing left to do out-of-order because all potential instructions are waiting for something in-order.
- djcapelis 13y agoThis isn't even a loop. But yes, the critical path and its dependencies is the main factor in determining the run speed of the instruction sequence unless your processor is balls crazy enough to value predict. ;) (It has never been successfully implemented, but a few papers have been written on it. There's actually some interesting possibilities that essentially involve value speculation and then forking an SMT thread and finding out whether or not to squash it later.)
- knappador 13y agoI'm so glad we're not talking about javascript ^____^