Mark Roulo (nothanks.delete@this.xxx.com) on October 30, 2020 11:42 am wrote:
> Jukka Larja (roskakori2006.delete@this.gmail.com) on October 30, 2020 11:29 am wrote:
> > Mark Roulo (nothanks.delete@this.xxx.com) on October 30, 2020 10:21 am wrote:
> > > Jukka Larja (roskakori2006.delete@this.gmail.com) on October 30, 2020 9:52 am wrote:
> > > > me (me.delete@this.me.com) on October 30, 2020 9:47 am wrote:
> > > > > > And I presume you are talking about AVX2. Both PS4 and Xbox One support AVX,
> > > > > > and that alone obviously didn't gather any significant support (even though
> > > > > > consoles have much more benefit from CPU optimizations compared to PC).
> > > > > >
> > > > > > -JLarja
> > > > >
> > > > > IIRC Jaguar's AVX isn't any faster than using SSE so devs mostly ignored it I guess.
> > > >
> > > > Is any AVX faster than SSE?
> > > >
> > > > -JLarja
> > >
> > > For my employer’s loads, AVX2 runs about 1.7x faster than SSE for compute bound loads.
> >
> > Yes, but that's AVX2, which is not available on Jaguar.
> >
> > -JLarja
>
> It is AVX2 because many of our loads are short integer loads.
>
> AVX won’t be faster on Jaguar than SSE because the Jaguar vector units are 128 bits wide so the AVX
> instructions needs roughly 2x the clocks per instruction which cancels out doing 2x more work per op.
>
>
> I would expect AVX implementations that are 256 bits wide (eg. Sandy
> Bridge) to run ~1.7x faster than SSE on floating point code.
>
> The slowdown is AMD specific (and only on some cores), not inherent with AVX.

Thanks, I recalled falsely that AVX had only 128 bit registers (like SSE) and was thus pretty much useless (though I guess it's supposed to be more compiler friendly).

Anyway, the fact that even AVX (non-2) on many CPUs offers twice the bandwidth, yet gathers no interest from game developers, just points more directly that SIMD extensions aren't interesting in the field.

-JLarja