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Date: Sat, 14 Feb 2015 10:23:53 +0000
From: Justin Cormack <justin@...cialbusservice.com>
To: musl@...ts.openwall.com
Subject: Re: What would make musl 1.2?

On 14 February 2015 at 00:06, Isaac Dunham <ibid.ag@...il.com> wrote:
> On Fri, Feb 13, 2015 at 11:09:55AM +0000, Justin Cormack wrote:
>> mips n32 - this seems to have mostly bypassed linux and android alas,
>> with only gentoo supporting it, despite the o32 ABI being horrible.
>> But Musl users should be encouraged to use n32 if building form
>> scratch...
>
> I've looked repeatedly, but everything I found has seemed to imply
> that n32 is like x32: a "32-bit" ABI that requires 64-bit hardware.
> Is this incorrect?

That is correct but as mips has been 64 bit since the 1990s a lot of
low end hardware has actually been 64 bit even in configurations that
are fairly low end. Also there are some floating point limitations in
o32. I guess as hardware specs rise that n64 support is probably more
useful than n32 for musl.

There is a rant about how terrible they all are here
http://www.linux-mips.org/wiki/WhatsWrongWithO32N32N64 suggesting
replacing the whole lot... the all code is PIC thing is certainly very
odd. Have found toolchain quality low too, but now at least
Imagination has people working on llvm and gcc etc.

>> mips n64 - there is a bit of cheap hardware around (Cavium stuff), but
>> fairly niche at present, although recent Android supports it and
>> Imagination seems to be promoting it more. Maybe they could be
>> persuaded to sponsor mips ports?
>
> They came out with a new MIPS64 processor design recently (no hardware
> is available yet), and the latest version of Android features MIPS64
> support. IIRC, Alexandru Voica commented that it usually takes a little
> under 2 years from design release to hardware on the market.
>
> I'd like to use musl on mips64, though I'm just a hobbyist and I've
> not yet found the cheap hardware to which you refer.

The cheap hardware easily available is:
Edgerouter lite http://www.ubnt.com/edgemax/edgerouter-lite/
(note the full ethernet performance requires binary blobs, and the USB
is fussy about what storage it will accept, so it is a bit annoying).
they make higher end hardware too.

All the Chinese mips chips (Loongson) are 64 bit. I dont recommend the
old 2F models (really odd instruction set) but the Loongson 3 ones
sound better. Apparently you can get them as systems/boards from China
for not too much and the newer ones are decent specs. I havent yet
tried this yet but may do. See the loongson-dev list for details eg
https://groups.google.com/forum/#!searchin/loongson-dev/loongson-3a$20mainboard/loongson-dev/twzd5TBz_1k/fZnJs5Xf_6QJ

I am hoping that now Imagination have realised that devs need hardware
there will be a 64 bit dev board in the next year or so, especially as
there was huge demand for the 32 bit one
http://blog.imgtec.com/powervr/mips-creator-ci20-development-board-now-available
- mine just arrived a couple of days ago.

Justin

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