Subject: re: dual boot for beige powermac G3
To: matthew green <mrg@eterna.com.au>
From: Bill Studenmund <wrstuden@netbsd.org>
List: tech-kern
Date: 07/22/2002 10:55:49
On Sat, 20 Jul 2002, matthew green wrote:

>
>    I have a beige G3, and there is not a dual boot loader that I've found.
>
> i don't know much about this topic, but i do know that the ppclinux
> booter (err, dunno it's name off hand) is able to dual boot macos
> (9 or X) and linux.  i don't see why it shouldn't be possible to do
> this with a smart enough ofwboot.

There are some more fundamental problems.

The biggie is MacOS and linux are happy with a quiesced (sp?) OpenFirmware
- they boot and tell it to shut down. Actually as I understand it, the
booter shuts it down. We however want OF up & running, a dangerous thing
in my mind as Apple (in contrast to other OF vendors) doesn't test their
OF in that mode. :-| It seems ok, so we might be fine. But we're a bit on
our own.

>    And I don't think we'll find one. Mainly as MacOS X and NetBSD have
>    different OFW boot requirements. MacOS X wants real-base set to -1
>    (ffffffff) while NetBSD wants it set to f00000.

We also need to do something about this problem. I'm not sure what exactly
"real-base" does for our boot, but for kernels over about 2 MB or so
(forgot the exact number), ofwboot just dies part way through loading if
real-base is -1. GENERIC crossed this threshold somewhere before 1.5 came
out, and we had lots of concerns that we'd broken the port. :-)

I'm not sure if all models suffer from it, but the older ones certainly
do.

>    real-base, then 'reset-all'. I'm aided by the fact I netboot NetBSD, so
>    disk partitions aren't a problem.
>
> i 4-way boot my G4/733 - linux, netbsd, macos 9 and X.  netbsd is the
> only one that doens't boot from the disk (yet), but macos9 and linux
> share one drive, and X and netbsd share another.  to boot linux or 9,
> i boot from hd0 and it gives me the linux bootloader.  X is the default
> boot, and netbsd requires "boot enet:0 ...."
>
>    MacOS X uses a boot partition to help load. I experimented with an
>    installboot that would move its boot partition before or after the MacOS X
>    one, so you could control which OS booted. But I didn't get it to work. I
>    now realize I had disk spin problems, so I should try again. :-)
>
> please! :-)

Note that this would only help older machines boot AFAIK as they are the
only ones that use installboot booting.

I played with the disk some more, and it turns out the problem is that it
wanted an ATN before it did anything. NetBSD and MacOS would send it one
as part of probe, but OF wouldn't. :-| With that disabled, I can boot
MacOS X directly.

Take care,

Bill