Re: [9fans] power pc port

[Charles Forsyth <forsyth@caldo.demon.co.uk>]

> AFAIK, SGI isn't publicly available. The last time I tried
> wrestling with SGI about it, they "poltely declined" to
> approve release of the source.

	...

>There's a lot of proprietary hardware inside the older SGIs.
>And I think you'd be hard pressed to find any documentation.

the silly thing is that there are or were linux ports
to several of the SGI devices that ran Plan 9 (and some others). certainly
i've got a copy of such a linux where the files are dated 1998.
if you've got the energy (which i suppose you might
if you've got the incentive of owning the appropriate hardware) you might
find an intelligent human being at SGI who will understand
that if linux exists for it, it is pointless preventing release of Plan 9
source for the same hardware.  unless, of course, they
are particularly astute and are trying to preven the
release of a readable system for that hardware.

alternatively, you could use the Linux code as a guide
to driving the hardware and re-port Plan 9.
it will be hard in the case of l.s and mmu.c because
Linux ever has had, as far as i can tell from arm and powerpc ports,
a remarkably x86-based approach to MMU
handling and Plan 9 takes a quite different approach,
especially on the multiprocessors.

it's a shame because the code in /sys/src/9/power/mmu.c
is a delight: clean multiprocessor mmu handling by wielding
logic (eg, carefully worked out invariants) rather than
sledgehammers (eg, interprocessor traps, locks and signals).
i used a variant on the bebox for that reason.
that code isn't SGIs.  i thought it was a good example to study
in an OS class.