On Thu, 3 Oct 2019, Maciej W. Rozycki wrote: > > You need an extremely high resolution timer to detect slight differences in > > execution time of speculatively-executed threads. The VAX 11/780 certainly > > did > > not do speculative execution, and my guess is that all VAXen did not, > > either. > > The NVAX and NVAX+ implementations include a branch predictor in their > microarchitecture[1], so obviously they do execute speculatively.
For the record: in NVAX prediction does not extend beyond the instruction fetch unit (I-box in VAX-speak), so there's actually no speculative execution, but only speculative prefetch. Maciej
