Bizarre GS hardware problem?

[taob@ionews.io.org (Brian Tao)]

    I have a problem with the usergroup's Apple IIGS and I hope someone
here has a solution (hope this is the right category and topic).  First,
the hardware:

Apple IIGS ROM 01
RamFAST rev. D, 256K cache, 3.01b ROM's
Conner 120-meg hard drive
PLI Infinity (InSite) floptical
Chinook RAM4000 4-meg RAM card

    Everything except the GS itself is mine.  I moved them over from my
computer to the club GS.  Everything checks out in my system.  But when
I plug the cards into the club GS, it won't boot GS/OS!

    The details:  I have not been able to get GS/OS to boot.  Usually
one of four things happen:

1. The GS/OS boot thermometer comes up, but after travelling about 6
pixels, it stops and hangs.  No beep, nothing.  It just freezes.  This
happens about 60% of the time.

2. Sliding Apple fatal error screen saying "Unable to load GS.OS file,
error $002D/$0045" (error code varies).  If I boot into ProDOS 8 and
fire up Cat Doctor, the file is there and it verifies properly.  Again,
there is nothing wrong with my System folder since it boots without fail
on my own GS.

3. Text dialog saying "Error $110A occured while trying load startup
FST".  Restarting is the only option.

4.  Sliding Apple fatal error screen $0308.


    It boots fine from a 3.5" floppy, but it hangs at the Finder before
it draws the hard drive icons.  I can boot into ProDOS 8 from the hard
drive, but mysterious crashes still occur (although less frequently). 
For example, it took me three tries to run ANSIterm before it made it
all the way to the terminal screen.  It has never crashed on startup
before.

    The GS passes the power-up self test.  I've tried swapping ROM chips
from two other computers, without success.  At an earlier UG meeting,
some combination of CPU/ROM chip swapping allowed it to boot System
6.01, but I cannot reproduce that result now.  Neither System 5.04 nor
System 6.0 work from the hard drive.

    When I OA-Control-Reset to reboot, a pattern appears on the text
screen which isn't present on my GS.  It looks like this (only bigger,
at full screen):

@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@@@@@@@@@@@@@**************
@@@@@@@@@@@@@@**************
@@@@@@@@@@@@@@**************
****************************
****************************
****************************

    The @'s are printed in inverse and the *'s are actually the Delete
key checkerboard character.  This flashes on the screen on powerup, just
before the Apple IIGS copyright screen takes over.

    The random nature of these errors makes it difficult to pinpoint a
single bad component.  Normally I would immediately suspect the hard
drive and/or RamFAST, but they both work perfectly if I replace them in
my GS (also a ROM 01).  I've tried changing the TWGS and DMA options on
the RF, but nothing works.

    I would really like to have this resolved by the next UG meeting
this Tuesday.  Is there anything else I should try?


[Followup, a few hours later]

    The problem is still here, and I've tried everything I can think of.
I've swapped 65816's, the GS ROM, the RamFAST ROM (3.00k and 3.01b),
even the long chip down by the Molex (sound GLU?  Ensoniq?) since I had
an extra one lying around.  I switched the RamFAST around to different
slots.  I tried booting of the floptical (which normally works).  I took
the floptical offline.  I took the hard drive offline.  Nothing.

    Booting from the 3.5" drive works like it should.  All the FTA demos
I have ran perfectly.  No crashes, no stray pixels on the screen, etc. 
So at least *those* work.  Nothing involving the SCSI card seems to work
properly, even though it works great on my own GS.  Ideas or comments?

-- 
Brian Tao:: taob@io.org (Internex Online, 416-363-3783, 27 lines, v.32bis)
::::::::::: 90taobri@wave.scar.utoronto.ca (University of Toronto, 9T4)