PET 3032 issue

From: Francesco Messineo <>
Date: Fri, 3 Feb 2017 13:35:56 +0100
Message-ID: <>
Hi all,
I made no real progress on the 3032 so far. Using the pettester.bin
image (is on it seems that the RAM is good (I get a
screen full of g's, alternating with the all characters screen). So
the kernel ROM is addressed correctly.
I could exclude the CPU (I have a spare one) and the ROMs. I
substituted kernel and both basic ROM's sockets too, however I have
continuity on all pins, so it wasn't strictly needed.
16 to 1 decoder looks as it's working, when the CPU enters a loop, I
see it's cycling on most of the ROMs. Address buffers (LS244) looks
good too, but I lack a logic analyzer to really have a good picture of
what's going on :(
Data path must be ok, otherwise there're few chances that the
pettester.bin could work.
The stock kernel gives a completely black screen most of the times (it
clears the video ram, then gets stuck somewhere or enters a loop
displaying a few characters).
Next try will be swapping the ram bank's CAS lines as this problem is
starting to smell like RAM addressing error or mirror (not detected by
the simple pettester.bin).
I'm tempted in writing a custom ROM to make tests easier, but maybe
someone else already made debug ROMs for the PETs?
Any hint is welcome anyway :)

Frank  IZ8DWF

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Received on 2017-02-03 13:00:02

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