ZombieLoad: Cross Privilege-Boundary Data Leakage on Intel CPUs

Re:ZombieLoad: Cross Privilege-Boundary Data Leakage on Inte... by tomxor on Tuesday May 14, 2019 @08:18PM (#19915175)

> Also I believe that 486 already had branch prediction

I can't find any evidence to support that [1]

I suppose it's technically possible to have branch prediction on a scalar processor, but I imagine it would not be hugely beneficial.

https://books.google.com.sg/books?id=QzsEAAAAMBAJ&pg=PA59&lp...

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Re:ZombieLoad: Cross Privilege-Boundary Data Leakage on Inte... by gpderetta on Tuesday May 14, 2019 @08:32PM (#19915276)

So it seems that the 486 had a trivial not-taken predictor; but that's still different from stalling on each conditional branch and does require checkpointing and rollback on misprediction (although with a pipeline only 5 deep that's probably also not very complex).

Edit: pentium did have a significantly more sophisticated predictor of course, although not without flaws.

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