Re: IIGS ROM1/ROM3?

[dempson@actrix.gen.nz (David Empson)]

Greg Weston <gwestonREMOVE@CAPSattbi.com> wrote:

> In article <1f6hun1.mxukpi1tuurggN%dempson@actrix.gen.nz>, David Empson
> <dempson@actrix.gen.nz> wrote:
> 
> > ROM 0 isn't supported by IIgs System 4.0 or later, and therefore isn't
> > supported by most IIgs applications released after 1988.
> 
> That doesn't seem to be accurate; I put the last version of GS/OS on my
> ROM 0 machine.

This is surprising to say the least.

I don't think I tried running anything more recent than System 4.0 on a
ROM 00.  I still have the ROM chip, but I don't really want to install
it in a machine, and as Bernie ][ the Rescue doesn't support ROM 00, I
can't easily test it myself.

With System 4.0, attempting to boot on a ROM 00 produced a text message
very early in the boot process (before the graphical splash screen)
saying that you had to upgrade the firmware to ROM 1 to be able to use
GS/OS.

Since the operating system no longer supported ROM 00, Apple removed the
toolbox firmware patch file for ROM 00 (*/System/System.Setup/TS1),
meaning that System 4.0 will only patch the firmware for ROM 01 (via the
TS2 file).

System 5.0 added support for the ROM 3, along with a TS3 file with ROM
patches.  (You can boot System 4.0 and earlier on a ROM 3, but the
operating system won't patch the firmware.)

Having a look through the key GS/OS boot files for System 6.0.1, I
cannot see any sign of the error message about requiring ROM 1.  (I
would have expected it to be in the PRODOS file in the root directly,
but I also looked in Error.msg, Start.GS.OS, GS.OS and TOOL.SETUP.  I
don't have a copy of System 4.0 or 5.0.x handy to my Mac, so I can't
quickly check for the presence/location of this error message in earlier
OS versions.)

It is possible that they removed the explicit check, instead relying on
the absence of the TS1 file (which should produce an error message when
TOOL.SETUP loads - it does if TS2 is missing on a ROM 1, for example).

If this is the case, then you might be able to to get a recent IIgs
system version working on ROM 0 by copying the TS1 file from System 3.2.
I'd regard this as a highly dubious arrangement, which is likely to be
missing more recent bug fixes and any new features which were added in
later system versions (in particular, QuickDraw and the Event Manager
had some pretty significant upgrades in System 5.0 and later).

The only way I can see this working reliably would be if Apple had
modified TOOL.SETUP to recognise ROM 00 and incorporating the ROM 00
patches into the TS2 file.

I was a member of APDA from about the time System 3.2 was released, and
have all the release notes for this and subsequent releases of the
system software.  I don't recall seeing any mention of support for ROM
00 being reinstated in System 5.0 or a later version.

-- 
David Empson
dempson@actrix.gen.nz