[libre-riscv-dev] openrisc1200

[Adam Van Ymeren]

On 2020-01-21 10:16 AM, Jacob Lifshay wrote:
> On Tue, Jan 21, 2020, 02:42 Luke Kenneth Casson Leighton <lkcl at lkcl.net>
> wrote:
>
>> https://libre-riscv.org/3d_gpu/arch_comparison/
>
> I added data for a lot more aspects. I think that we should go with
> OpenPower due to several aspects:
>
> we should try to keep our messaging more consistent, continuously changing
> which ISA we will use will cause people to not think we will ever complete
> anything

While I agree it may hurt the reputation a litttle, I think doing that
should only be one small factor in the overall decision.  The reputation
damage of another ISA change I think is does far less damage than
committing to the "wrong" ISA.  We should be worried about the next
several person years of developments and what ISA would play well with
our customers.  We don't want to fall into a sunk cost fallacy of
worrying too much about the reputation in the community of people who
read Phoronix, when we're talking about selling millions on units to
companies who probably couldn't care less what the Phoronix discussion
forums said about the project 2 years ago.  Plus this exercise of doing
a detailed evaluation/comparison on the wiki means we can point
detractors to this wiki page and say "Look!  We've done our due
diligence, and can strongly justify why we've done what we've done,"
regardless of the final decision

As the saying goes, the best time to do this evaluation was 2 years ago,
the second best time to do it is *now*.

>
> Power has a huge software ecosystem, probably larger than all of RISC-V,
> MIPS, and OpenRISC combined. Probably the 3rd largest in the industry after
> x86 and ARM. This is probably the biggest factor for which ISA to pick.
>
> Power is known to be very suitable for high-performance CPUs (Power9).
>
> OpenRISC doesn't seem to be a viable option due to the lack of support for
> 64-bit in software (linux, probably others), among other reasons.

Looking at the table now, I think no-JIT for V8 and Java are a big
deal.  I suspect that V8/Chrome are very popular with the high volume
customers we might get.  Infotainment systems in TVs/Cars/Planes are
usually driven by some sort of WebUI or Android.  So that's points for
POWER.

None of them have Android support which is another high volume use
case.  Our SoC is likely to be very popular with cheap android phones if
we can get Android support, similar to the market MediaTek services but
we have the advantage of being libre, which MediaTek is nowhere close
to.  If we can guess which platform Google is more likely to add support
for, that would be a useful input, but Google tends to be fairly
unpredictable on what they will choose to focus on.