He doesn’t list what the mistakes will be. He said that he fears that because hardware people aren’t software people, that they will make the same mistakes that x86 made, which were then made by Arm later.
He did mention that fixing those mistakes was faster for Arm than x86, so that brings hope that fixing the mistakes on Risc V will take less time
No, it was about the prediction engines that contain security vulnerabilities. Problem is that software has no control over that, because hardware does future predictions for performance optimization.
Prediction is a hard problem when coupled with caches. It relatively easy to say that no speculative instruction has any effect until it’s confirmed taken if you ignore caches. However caches need to fetch information from memory to allow an instruction to evaluate, and rewinding a cache to it’s previous state on a mispredict is almost impossible. Especially when you consider that the amount of time you’re executing non-speculative code on a modern processor is very low.
Not having predictions is consigning yourself to 1990s performance, with faster clocks.
He doesn’t list what the mistakes will be. He said that he fears that because hardware people aren’t software people, that they will make the same mistakes that x86 made, which were then made by Arm later.
He did mention that fixing those mistakes was faster for Arm than x86, so that brings hope that fixing the mistakes on Risc V will take less time
I think it was something with instruction sets? Pretty sure i read something about this months ago.
No, it was about the prediction engines that contain security vulnerabilities. Problem is that software has no control over that, because hardware does future predictions for performance optimization.
Aah, right, that.
Prediction is a hard problem when coupled with caches. It relatively easy to say that no speculative instruction has any effect until it’s confirmed taken if you ignore caches. However caches need to fetch information from memory to allow an instruction to evaluate, and rewinding a cache to it’s previous state on a mispredict is almost impossible. Especially when you consider that the amount of time you’re executing non-speculative code on a modern processor is very low.
Not having predictions is consigning yourself to 1990s performance, with faster clocks.
I mean, that’s all chip architectures are, so yes.