Re: ROM 3 Questions

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

william strutts <wrstrutts1@home.com> wrote:

> "Mitchell Spector" <a_specto@alcor.concordia.ca> wrote in message
> 3b43e3fd.18187324@newsflash.concordia.ca">news:3b43e3fd.18187324@newsflash.concordia.ca...
> > dempson@actrix.gen.nz (David Empson) wrote:
> >
> > ---------Begin post clipping------------------------------------------
> >
> > Differences between the two versions of the ROMs in the ROM 3 IIgs
> >
> > by David Empson (dempson@actrix.gen.nz)
> >
> > Apple released two sets of ROMs for the "Apple IIgs with 1 megabyte of
> > memory", popularly known as the "ROM 3 IIgs".
> >
> > The original set of ROMs has the serial numbers 341-0728 and 341-0729.
> > These are very rare: I only know of one IIgs that has been confirmed
> > to have these ROMs.  [Make that two now]
> >
> > The revised ROMs have the serial numbers 341-0748 and 341-0737.
> > These are by far the most common.
> >
> 
> I now have three ROM 3 boards:
> 
> Machine 1:
>   341-0748 (28 pin plastic ROM chip)
>   341-0728
> Machine 2:
>   341-0748 (32 pin PROM/EPROM plastic package)
>   341-0737
> Machine 3:
>   341-0749 (32 pin EPROM ceramic package)
>   341-0728
> 
> Sorry if this mucks up the waters.

Talk about throwing a spanner in the works.  I hadn't heard of a
341-0749 ROM before.  The higher number implies it is newer than the
main ROM 3 release (341-0748 and 341-0737).

Perhaps this is the mythical ROM 4?

> Was there some kind of field bug fix that might have happened on the
> machines since they don't conform to the quoted statements above?
> The ones with the 341-0728's should also have the 341-0729's as well
> but the two that do have it have different ROM's.

As noted in my old post, 341-0728 is identical to 341-0737, so there is
only one ROM to investigate.  The changes from 341-0729 to 341-0748 are
known.  The only question is what changed between 341-0748 and 341-0749.

I can't say anything about what might be in this 341-0749 ROM unless I
can get hold of a copy of its contents and repeat my earlier
investigation, comparing it to the 341-0748 ROM.