Re: Original IIgs ROM

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

Paul Grammens <grammens@svn.net> wrote:

> I followed David Empson's directions and extracted the ROM firmware from my
> IIgs with the original ROM. It's in 4 parts. What's the most useful way to
> archive this- as a .zip file, .shk, or what?  I guess people with ROM
> burners or emulators would be the ones interested in this, but I don't have
> either, so I'm not sure what they need.

I'd suggest concatenating the four files and saving it as a binary image
(128 KB).

If you intend to burn a physical ROM from this, my recollection is that
the high order address bit to the ROM is inverted on the original IIgs
motherboard, which means that bank FF goes _before_ bank FE in the
physical ROM.  This isn't obvious from the circuit diagram, but I think
I discovered it when I tried to read the ROM in an EPROM programmer.
(This would apply to both ROM 0 and ROM 1.  I've never looked at the
innards of ROM 3 in this manner.)

If you intend to use the ROM image with an emulator, I expect that the
banks should be in the normal order (FE first, then FF).