Maynard Handley (name99.delete@this.name99.org) on October 10, 2020 10:36 am wrote:
> hobold (hobold.delete@this.vectorizer.org) on October 10, 2020 8:58 am wrote:

[...]
> > But one cannot reduce latency below zero (no matter what marketing departments
> > say), so these gains are not very likely to be repeated by AMD.
>
> Yes you can :-) Value prediction is real, and done competently provides genuine speedups...
> As far as I can tell no-one is doing value prediction yet (as always asterisk against Apple...)
> but it's still a promising technology once everything easier has been done.

Latency is the time you must wait for an unknown result that will be produced in the future. Value prediction is re-use of a known result that has been produced in the past.

It is possible to try and guess the future. It is not commonly possible to reliably violate causality (in the macroscopic world).

I do not mean to diminish all the ingenious speculative algorithms. But for the benefit of the lurking readers, I want to re-iterate that latency times are always strictly greater than zero.

No matter what marketing departments or internet discussion forums say. :-)