Re: Different versions of the ROM 3 IIgs - details

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

In article <3bbqht$mh1@apple.com>, David A Lyons <dlyons@apple.com> wrote:
> 
> "Released" is too strong a word here...there is only one real ROM 3
> version.  Paul Bauer's GS is the only one I know of in the Real World to
> have the bad version.

Glad to hear of it.  There was some discussion about this a few months
ago here (regarding the imagined "ROM bug" that causes the programmer's
CDAs to appear on some ROM 3s), and someone else claimed to have a
nonstandard version of the ROMs.  I asked them to provide part numbers
from the ROMs, but never got a reply.

> Excellent work!  You got it exactly right.  To clarify:  Yes, the word
> you guessed is just a checksum is exactly that.  The problem with ROMDISK
> was that no calls were allowed through until it had been initialized by
> an INIT call, but even the INIT call was not allowed through.

I thought it might be something like that.  The ROM 1 doesn't check
for any flag memory location, so I expect it lets any call through if
the ROMDISK ID bytes are there.

> This went unnoticed until the last minute because nobody had actually
> built a ROMDISK card for the ROM 3 machines earlier.

There were already ROMDISK cards that worked with the ROM 1, e.g. the
OctoRAM ESP (which I have).  Perhaps you mean that there weren't any
commercially available ROMDISKs at the time (earlier ones were out of
production). 

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand