RE: PET 2001 fix Part 3 - RAM/ROM board etc.

From: Baltissen, GJPAA (Ruud) <>
Date: Mon, 16 May 2011 09:25:59 +0200
Message-ID: <>
Hallo Philip, 

> I just replaced the CPU, unfortunately there was no change whatsoever.

I already was afraid that this would be the case but it was at least the
most easiest thing to check.

First some questions:
- can you program in ASM and produce BINs?
- you can program EPROMs, can you program EEPROMs as well?
- if yes, do you have EEPROMs laying around?
- if yes/no or no/no, do you have enough EPROMs laying around?
The reason for these question, we know my little program works fine so
the next thing you should do IMHO is to step things up. 

You could start with a little program that checks various things like
the RAM (at least Zeropage + stack) and the hardware (6522, 6520, etc.).

Another thing I'm curious about is what happens around the last and
first columns. First only fill the first page with 0..$FF. Then check
the columns by copying the addresses $8000+$4C to $54 to somewhere in
the next page in the middle of the screen, for example from $8128 on. If
you see 'lmnopqrst' then this would mean that the video RAM is written
with the correct valus and the display circuit is to blame. But if you
see 'ghijhhijk' again then would mean IMHO that the filling of the video
RAM already went wrong.

You see, enough work to do :)

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Received on 2011-05-16 08:00:18

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