lurker (lurker9000.delete@this.realemail.mail) on October 30, 2015 5:56 am wrote:
> dmcq (dmcq.delete@this.fano.co.uk) on October 30, 2015 5:12 am wrote:
> > I think 256 bits would be better as you can do four double precision operations at once and that is quite
> > common. On the other hand with four SIMD units instead one could merge two operations to give an effective
> > two by 256 bit units except for some special operations.
>
> 256 bits would be ideal, but I don't think 128 bits is going to be terrible for general
> applications. A lot of software don't even use AVX instructions. And as you said the
> four pipes can merge to execute 256 bit ops so at least that's something.
>
> > For anything larger they'd probably be better
> > off relying on GPUs I think if they can get the coherence and message passing working well. I can see
> > how to save larger register sets without impacting interrupt handling too badly but it seems a lot of
> > work when ARM is probably hoping to move 64 bit ARM into the embedded processor market.
>
> That reminds me, isn't AMD working on an HPC APU? Perhaps they decided that more intense workloads
> will be offloaded to the GPU anyway so they didn't bother that much with beefier FPU?

Thinking about it I would guess ARM will eventually put in some 256 bit operations which act on a pair of SIMD registers at once rather than extending the SIMD registers, that is what they did for ARMv7 to get 128 bit using 64 bit registers.