The bug allows attackers to swipe data from a CPU’s registers. […] the exploit doesn’t require physical hardware access and can be triggered by loading JavaScript on a malicious website.
The bug allows attackers to swipe data from a CPU’s registers. […] the exploit doesn’t require physical hardware access and can be triggered by loading JavaScript on a malicious website.
These would be performance regressions, not correctness errors. Specifically, some false dependencies between instructions. The result of that is that some instructions which could be executed immediately may instead have to wait for a previous instruction to finish, even though they don’t actually need its result. In the worst case, this can be really bad for performance, but it doesn’t look like the affected instructions are too likely to be bottlenecks. I could definitely be wrong though; I’d want to see some actual data.
The pentium fdiv bug, on the other hand, was a correctness bug and was a catastrophic problem for some workloads. It was absolutely detected - it was found outside of Intel!
Thanks for the clarification!
I remember having to learn about fp representations in a numerical analysis class and some of the things you had to worry about back then, but by the time I ended up doing work where I’d actually have to worry about it, most of the gotchas had been taken care of so I largely stopped paying attention to the topic.