[Arm-netbook] Libre RISC-V SoC

Bill Kontos vkontogpls at gmail.com
Mon Jan 22 20:38:26 GMT 2018

On Fri, Jan 19, 2018 at 6:06 PM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:

> i'm also talking to jeff from nyuzi, he designed a software-driven
> "compute engine that happens to be reasonably good at 3D", the
> interesting bit being that he's focussed on working out which areas
> need performance improvements.  this is something that's almost
> completely lacking in the published academic world... *because nobody
> in the academic world has designed and published a GPU!*
> we worked out that nyuzi is approximately 1/16th the speed of MALI400.
> roughly.  although area-for-area it's quite hard to tell whether
> that's a fair assessment because you can't *get* die areas for MALI400
> (anyone know anything better than these estimates?
> https://forum.beyond3d.com/posts/1176110/ ) and it's the performance /
> mm^2 / watt that's critical, we worked out that if you put in 2 nyuzi
> cores and managed to halve the number of instructions / pixel by
> replacing critical path blocks with hardware-rendering ones, you'd end
> up at about 25% the performance of MALI400 and that i feel would be
> "good enough" for a first version.  i'd be interested to hear what
> people think, here.

That would by no means be enough. We need video decoding blocks,
without those the SoC is as good as an rpi for e.g. the education
market that you have mentioned and I'm sure not interested personally
on using a system as a desktop/laptop that can't play videos without
stuttering while potentially doing something else at the same time.
And I'm not even talking about games here. I don't know if there is a
simd extension on the cpu cores that someone can write a real time
decoder for and hook it up to whatever's needed for firefox etc to
automatically redirect to( not that that's an easy thing), but 25% of
an outdated low performance gpu sounds really low to me. What's the
point of having such an awesome low power core if we can't use the
thermal envelope for pushing graphics?

> the *general-purpose compute* performance of nyuzi on the other hand
> is really good.

What is gpgpu used on desktops right now for?

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