Re: ROM 3 //gs issues

[Tom Greene <tom@cowgod.org>]

On Sep 12, 11:36 pm, Nels Bruckner <ne...@comcast.net> wrote:
> 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 ofhttp://www.reactivemicro.com/product_info.php?cPath=1_36_46&products_...
> out there somewhere...?
>
>      --Nels

I hacked together a ROM 3 checksum program using a CRC32 routine from
6502.org.  If you'd like to give it a try, it is available here:
http://cowgod.org/apple2/romchecker.dsk.gz

I'm sure Henry at Reactive would make a set of ROMs for you, if you
ask him.

Tom