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Re: request for help to make powerpc custom boot disks

Ethan Benson writes:

> what part of:
> Mail-Followup-To: debian-powerpc@lists.debian.org
> Mail-Copies-To: nobody
> X-No-CC: I subscribe to this list; do not CC me on replies.
> don't you understand?

1. it is in the headers instead of the signature
2. it isn't handled by my crufty old UNIX mail program

Have you written a mail program that interprets X-No-CC ?

> you demonstrate how little you know about how OldWorld Macintoshes
> work.

You have forever destroyed my innocent faith in the beauty
of Apple hardware. Shame on you!  :-(  I now declare the
modern PC architecture to be a coherent and efficient design.
Even the A20 line and MBR are looking good now.

> first there are two firmwares in OldWorld PCI macs, the first is
> OpenFirmware, an extremely and hideously broken implementation of
> OpenFirmware, on most machines its either not capable of reading the
> disk at all, or can barly read it.

An aborted attempt to switch? It makes no sense to even have
the OpenFirmware code if it isn't used.

> the next is a 4MB ROM with the core of MacOS burned onto it (on very
> old macs this was actually complete enough to boot without any other
> media).

This is 680x0 code too, isn't it?

> it then checks the hard disk, the very first thing it checks on a hard
> disk (or CD) is the Driver descriptor map (block 0 of the partition
> table) this contains a list of MacOS disk drivers installed on the
> disk (in Apple_Driver43 partitions), if no drivers are found the ROM
> code rules the disk unbootable and irrelevant, thus ignores it[0].  if
> the drivers are found the code in them is loaded to replace the disk
> drivers that were burned into the ROM (since they are usually broken

On a new system, with "ROM" coming from an HFS partition,
the driver partitions make no sense at all.

> now its certainly possible for a disk driver to be written which is
> free software, or even pretends to be a driver but really acts as a
> bootloader, but nobody is all that interested in learning and coding
> such a beast, besides that if you ever boot MacOS it may overwrite
> this driver to `update' it (macos upgrades typically do this), a fake
> driver would probably interfere with use of MacOS at all, but if you
> wanted a macos free machine that wouldn't matter i suppose.

One would want to make the bootloader be a wrapper that can
supply the old driver when booting MacOS, and then write a
MacOS program (extension?) to fix up the bootloader at shutdown.
Yeah, fat chance anyone would.

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