Fwd: VAX + Spectre

[Maciej W. Rozycki]

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