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Re: PowerMac support



On Mon, Apr 24, 2000 at 12:25:19AM -0500, w trillich wrote:
> Bob Kuo wrote:
> > 
> > Dear PowerMac users,
> >     I looked over the support page for PowerMacintoshes, but i have not found
> > all of the information I require. Do you support PowerMacs 8100s? I saw that
> > almost all of the other PowerMacintoshes were supported, but 8100s were not
> > listed as one of the supported one.
> 
> according to the previous exchange, there's a debian available for
> 68000 macs; and it's my understanding that the powerpc chips emulate
> the old-standard 68000 instruction set, so maybe this'll work for you,
> too... linux--a great way to keep the older macs crankin'!

not exactly, the powerpc chips do not emulate the 68000 instruction
set, what you are thinking of is the MacOS 68K emulator..

all the older powermacs (all until very recently) had a 4MB hardware
ROM with low level MacOS software, called the `toolbox' it contained
alot of the code that would belong in a kernel such as the binary
loader.  This ROM included a 68K emulater for MacOS 68K binaries.
Since Linux does not use the MacOS hardware ROM this emulater is not
available, furthermore the emulater was designed to run MacOS binaries
and probably could not be made to run ELF binaries anyway.

the newwer PowerMacs no longer have a hardware ROM containing the
MacOS specific cruft, instead they have a smaller 1MB boot ROM
containing a broken version of OpenFirmware, MacOS now has a ELF
bootloader which copies an image of the old 4MB hardware ROM into RAM
where its executed and continues booting macos just as it always did
in hardware.  

(note all PCI powermacs have OpenFirmare, its in a separate ROM from
the MacOS ROM, on oldworld powermacs OpenFirmware executed the code
in the hardware MacOS ROM which booted MacOS)

-- 
Ethan Benson
http://www.alaska.net/~erbenson/

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