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

From: Philip Lord <>
Date: Mon, 16 May 2011 17:00:15 +0900
Message-id: <>
> - can you program in ASM and produce BINs?
Unfortunately I have no skill at all in 6502 (or any other kind) assembler :-(

> - you can program EPROMs, can you program EEPROMs as well?
I have an Needhams EMP-20 programmer and a stack of 2708, 2716, 2732, 2764, 27256, 27512 and 2532's (maybe about 8 of each type)

> - if yes, do you have EEPROMs laying around?
I might have a 59V65A (28C64 equivalent) somewhere, but I couldn't get it working for what I bought it for (ZX1541). I ended up resorting to a real 28C64 and it it might be dead!

> - if yes/no or no/no, do you have enough EPROMs laying around?

I have plenty of EPROMs

> 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 :)
Sure is...but unfortunately none of the above means much to me as I have no assembler skills at all...I can understand basically what you are describing, but the technical aspect just sounds like martian :-o

Now I mentioned before that I didn't have a scope...actually I was lying. I do have an old Kikusui 20mhz COS 5020 that was given to me. I have never used a scope before or know how to use one exactly (I understand the basic principle of course). So I've just pulled it out of it's box incase it comes in useful. I have just tested it for a square wave, and It seems to work, but the beam tends to wander from time to time, but should be ok.

Thanks again.


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Received on 2011-05-16 09:00:13

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