RE: Vet for a PET

From: William Levak (wlevak_at_cyberspace.org)
Date: 2002-09-03 07:38:26

On Mon, 2 Sep 2002, Bo Zimmerman wrote:

> 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.

Those are correct.

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

The calling location $E62E is the hardware clock interrupt.

What did you do about screen memory?  On the non-CRTC PET's the CPU waits
every 1/30 second for 1/60 second so the screen circuitry can generate
the screen image.  The address bus is being used at this time.  This is
controlled by the clock interrupt mentioned above.




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