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Re: ROM 3 //gs issues

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
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