> Like [..] CPU Branch Prediction Idiocy
Can you elaborate on that or point me to some sources as I thought branch prediction was a good thing for speed (until now)
See the CPU slowdowns and related security issues that resulted from branch prediction, basically CPUs would optimistically assume access and so could be tricked into executing what you wanted...which there was no OS or security level control that could be used to fix that.
They had to patch "micro code" to turn off the branch prediction in order to fix the security issues, which if they hadn't had that basically a ton of institutions would have been SOL (think banks unable to patch security holes in their computer systems - bodes poorly if you also realize banks aren't usually able to patch their systems overnight).
While the summary in this reply is at best misleading if not simply wrong, the linked Wikipedia article is good. I recommend just reading that article and disregarding the comment.
Also yes, branch prediction is "a good thing" without which processors wouldn't be able to reach the performance they have today. Starving the whole instructing pipeline at every branch for dozens of cycles is not great.
Even the processor on the BCM2835 used in the first raspberry PI had branch prediction, and for good reason.
smaudet|2 years ago
https://en.wikipedia.org/wiki/Spectre_(security_vulnerabilit...
They had to patch "micro code" to turn off the branch prediction in order to fix the security issues, which if they hadn't had that basically a ton of institutions would have been SOL (think banks unable to patch security holes in their computer systems - bodes poorly if you also realize banks aren't usually able to patch their systems overnight).
chmod775|2 years ago
Also yes, branch prediction is "a good thing" without which processors wouldn't be able to reach the performance they have today. Starving the whole instructing pipeline at every branch for dozens of cycles is not great.
Even the processor on the BCM2835 used in the first raspberry PI had branch prediction, and for good reason.