juanrga (noemail.delete@this.juanrga.com) on October 29, 2016 10:15 pm wrote:
> Simon Farnsworth (simon.delete@this.farnz.org.uk) on October 28, 2016 6:19 am wrote:
> > juanrga (noemail.delete@this.juanrga.com) on October 28, 2016 2:02 am wrote:

> > >
> > > Essentially the same rule applies upwards and downwards, only parameters vary.
> > >
> > > If your design is optimized for 4GHz and underclocking to 2GHz increases the IPC by less than 5%, then
> > > if your design is optimized for 2GHz, overclocking it to 4GHz will reduce the IPC by a similar amount.
> >
> > The same rule does not apply upward and downward. If it did, I could reliably overclock
> > a Pentium III to 4 GHz, just as I can downclock a modern Intel chip to 800 MHz.
> >
>
> I didn't wrote "the same" but "Essentially the same" and I mentioned explicitly
> that parameters vary (critical path timing, clock skew, jitter...).

If "works" versus "not works" is "essentially the same", then I'd rather not work with any product you engineer.

It's a massive difference - it's not just "parameters vary", it's that you cannot take a circuit with a critical path of 20 FO4 delays, and then clock it so rapidly that it only has 10 FO4 delays in which to stabilise - it will simply fail to operate reliably.