[brucedawson]

Author here: This is not a common problem. I think I was told that Alpha had basically the same bug but it is a bug, for sure. Speculative execution causing problematic side effects is a deal killer.

Speculative execution, however, can cause less problematic side effects. For instance, a speculatively executed load or prefetch will usually actually prefetch which will pollute the cache, TLB, etc., and reveal side-band information, but that is a performance problem and perhaps a subtle security flaw, not a correctness bug like this was.

[MBCook]

I remember reading this many years ago, it was great.

In the last week Raymond Chen on his The Old New Thing mentioned the concept of delay slots on some CPUs.

It sounds like a similar thing, just formalized so it’s not a bug. Knowing that the instruction after a branch always executes, regardless of if the branch is taken.

Do I have that right?