Re: ROM 3 //gs issues

[Nels Bruckner <nelsb@comcast.net>]

On Sep 12, 6:52 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Nels Bruckner wrote:
> > On Sep 6, 2:33 pm, Linards Ticmanis <ticma...@gmx.de> wrote:
> >> Nels Bruckner wrote:
> >>> The next thing I could try is swapping in a second set of ROM 3 ROM
> >>> chips, which I don't have.  My usualy saviors in this kind of
> >>> situation, Reactive Micro, don't seem to carry ROM 3 replacements.
> >>> Any suggestions?
> >> On an 8-bit Apple I'd just write and run a quick Applesoft program to
> >> checksum the ROM (sum or EOR of all bytes), test it on an emulator and
> >> on the real system and see if the results differ.
>
> >> I don't know the IIgs well enough to know whether the entire ROM is
> >> readable from Applesoft. You might need assembly, but I assume it would
> >> be short enough to just enter from the CALL -151 monitor.
>
> >> --
> >> Linards Ticmanis
>
> >      Could certainly do that, but whether pass or fail it wouldn't
> > give me much new info.
>
> Actually, it will verify whether your machine is reading its ROM
> correctly, which is an issue.
>
> >      I did discover that the application failures I was seeing were
> > because (duh) I hadn't installed a RAM card in this machine.  Now that
> > the machine has 2MB of RAM it runs Dungeon Master, etc, just fine.
> > Which really just leaves me with the curious fact that the diagnostic
> > software reports a failure of the CPU/ROM validation step, since the
> > machine seems to function just fine.
>
> It's not hard to imagine a fault which the software you have tried
> does not "exercise", or which it tolerates.
>
> CPU/ROM validation must be very early in the self-test sequence, so
> most of the test may not even be running.
>
> >  I'm keeping my eyes open for a
> > second, dirt cheap ROM 3 machine (I think I got this one for $20+p/h)
> > to swap ROMS with but, in the meantime, anyone know where I can pick
> > up a set of ROM 3 chips?
>
> Running the checksum that Linards suggested, and comparing it with
> the same test run on an emulator configured for ROM 3 will answer
> the question of whether or not the ROM is bad.
>
> Swapping the processor is just as easy as swapping the ROM, and
> you can use any version of a IIgs for the swap.
>
> -michael
>
> AppleCrate II: An Apple II "blade server"!
> Home page:  http://members.aol.com/MJMahon/
>
> "The wastebasket is our most important design
> tool--and it's seriously underused."

     Actually, I'm using the Apple //gs Diagnostic disk to run the
tests - everything else (that I have hardware to test with) passes w/o
any failures, though obviously there could some fault in the ROM
related to any number of areas that aren't getting exercised here.
I've verified that the CPU is good (read above).

     In the event that one or both chips are bad, is there a source
for (new) ROM 3 chips?  Seems like there should be the ROM 3
equivalent of http://www.reactivemicro.com/product_info.php?cPath=1_36_46&products_id=136
out there somewhere...?

     --Nels