Dummond D. Slow (mental.delete@this.protozoa.us) on November 17, 2020 11:18 am wrote:

> It's simple: SMT. Had Apple implemented it, it would run away in Cinebench.
> Lesson to the people saying it's a pointless/stupid/doomed feature.
> Seems Renoir is able to bridge its "worse single-thread" and "worse
> manufacturing node" disadvantage pretty much thanks to SMT.
>
> Which also tells you where the biggest threat from Apple is. It pretty much caught
> up with state of the art x86's single core performance AND has process advantage.
> It could shoot ahead in performance in two areas if it chose to:
> 1) SMT as discussed. Not having SMT leaves massive multithread performance
> gains (end energy efficiency gains, more importantly) on the table.

SMT is a *terrible* idea for new designs. Sure, it gets you performance uplift, but it comes at a cost, particularly in terms of side-channel exposure. That is a game of whack-a-mole that doesn't end any time in the near future. Real cores that can be fed properly give you more deterministic performance without all of the other downsides from sharing resources.

Jon.