From: William Levak (wlevak_at_cyberspace.org)
Date: 2002-09-01 05:55:03
On Sat, 31 Aug 2002, Bo Zimmerman wrote:
> Hello Mr. Levak!
>
> I swapped the 6520s to no avail. I saw nothing overly strange about the
> user port: no strange wires or anything. I also confirmed the integrety
> of zero page memory by putting some values in through the ML monitor.
> Everything looks OK down there.
>
> It's really strange. That READY prompt appears whenever I try to "x" out of
> the monitor, the same as it does at power up. However, I still have that
> shortened screen at the top, and ANY entries drop to the monitor.
>
> Perhaps my spare KERNAL or BASIC ROMs were just as bad as the originals...
> I'll have to read those in.
>
> Do yall have any other ideas? I'm pretty clueless, but have learned
> something just from your suggestions!
The fact that you can get a ready prompt when you type X means that you
come up in the ML monitor. There only a couple ways to do that.
1) a jumper on the DIAG line on the user port.
2) A defective chip or short on the DIAG line.
3) execution of the BREAK instruction, $00.
4) Defective ROM, address line, or data line that causes instructions
to be garbled.
5) special ROM that comes up in ML monitor.
If you have another machine, you can check the ROM's against the funet
images.
You should also check the ROM part numbers against the information on
funet to be sure they are in the right sockets.
Checking address and data lines gets messy.
Bill
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