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From: Single Stage to Orbit <alex.buell@munted.eu>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: New Pico2
Date: Tue, 13 Aug 2024 10:22:19 +0100
Organization: One very high maintenance cat
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On Tue, 2024-08-13 at 08:40 +0100, Richard Kettlewell wrote:
> druck <news@druck.org.uk> writes:
> > On 11/08/2024 22:32, Single Stage to Orbit wrote:
> > > I've got a RISCV baremetal operating system I might bring up on
> > > this device but looking at the datasheet for the RISCV processor
> > > used, it's only got machine mode and user mode, no supervisor
> > > mode and no paging. It does not even support any of the Sv
> > > pagetables so that's a challenge.
>=20
> Also no floating point, if I=E2=80=99ve understood correctly?
>=20

I just had to re-check the datasheet and you're right, the Hazard3
cores do not handle floating point. That's deeply disappointing.=20

The M33 cores do support single and double precision floating point,
single floating point within the M33 cores and double precision maths
using one of its three coprocessors (gpio, maths and the other I
forget). I guess we could just ring the doorbell to get the ARM core to
do the maths for the Hazard3 core. :-D

> > The joys open "open source" CPUs with no standardised feature sets.
> >=20
> > > Most interestingly enough, you can actually boot up with one
> > > RISCV core and one ARM core, two RISCV cores or both ARM cores.
> > > Mixed processor cores that'll be fun to see what we can do with
> > > that.
> >=20
> > I think they did that for all the people who keep insisting they
> > should move to the "new future" of RISC V. Now they can find out
> > how badly it compares to a contemporary ARM core.
>=20
> It=E2=80=99s a slightly odd device, isn=E2=80=99t it?
>=20
> If you wanted to explore RISC-V then there=E2=80=99s more flexible option=
s.
> If you just wanted a microcontroller for something and didn=E2=80=99t car=
e
> too much about CPU architecture then the dual-architecture thing is
> wasted. Two entire CPU cores that you don=E2=80=99t get to use.

Yes the datasheet says the unused cores are gated off.=20
--=20
Tactical Nuclear Kittens