RE: Vet for a PET

From: Bo Zimmerman (
Date: 2002-09-02 10:12:46

Hello all!

Well, due to yalls suggestions, I have accumulated more information!

First off, I confirmed the integrety of the ROMs.  Strangely, my new
fancy-schmancy PC programmer wouldn't read those PET ROMs (as 2532s), so I
had to run back to my trusty Prominade C1 on the C128D.  Anyways, all the
ROMs (901465-01,02,03 and 901447-24) checked out, EXCEPT that the 901465-02,
at offset 60, had the value $c9 in mine, while the one off funet had a $c8.
Havn't yet looked into that, but its a possibility...

Second, I confirmed the locations of the chips, sort of.  My board does not
have the ROM sockets numbered (UD9, UD8, etc), so it was tough to confirm
against the docs on FUNET.  However, if you are facing the front of the
computer, they are (left->right), 901465-03, 901447-24, 901465-02,
901465-01.  If that corresponds with UD9-UD6, then they are OK.

And last, as Mr. Anderson suggested, I wrote down the monitor entry info.
It is:
007C E62E F1 Fc FF 01 F8

That means close to nothing to me, except that, if 007C is the break
address, and there is any correlation with the C64, that would be around the
same place as that little BASIC routine (CHRGET) in zero page.

As for Mr. Levak's suggestions, they are awesome places to start.  I think
I've eliminated #1, #4, and #5, since the fact that the ML monitor runs at
all should speak well for the address and data lines to the ROM (well, the
kernal, at least).  I suppose I will peek through to the BASIC ROMs directly
and see if they seem ok.  On #2, I suppose I can check for a short easily
enough, though a bad chip would be more difficult.  #3 seems easily the most
likely, and is undoubtedly tied in some way with the strange screen
behavior.  I know there is a PET memory map around here, but would finding
the screen length (24) in the proper zero page location really tell me much?
Isn't that all really enforced in the editor ROM??

Once again, I am very appreciative of yalls help.  Any other suggestions are
very welcome!

- Bo

> -----Original Message-----
> From:
> []On Behalf Of Larry Anderson
> Sent: Sunday, September 01, 2002 10:58 AM
> To:
> Subject: Re: Vet for a PET
> William Levak wrote:
> >
> > 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.
> If the monitor's status registers are there, it would tell where the
> program counter was at (where the instruction is that 'broke' you into
> the monitor or called the monitor).  From there you may be able to tell
> if it was suppoed to be a ROM routine, etc.  If there isn't status
> registers when it starts up, R should give them to you.
> >     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
> >
> >        Message was sent through the cbm-hackers mailing list
> --
> 01000011 01001111 01001101 01001101 01001111 01000100 01001111
> 01010010 01000101
>    Larry Anderson - Sysop of Silicon Realms BBS  (209) 754-1363
> 300-14.4k bps
>        Set your 8-bit C= rigs to sail for
> 01000011 01001111 01001101 01010000 01010101 01010100 01000101
> 01010010 01010011
>        Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail 2.1.4.