Re: 4032-2001N editor ROM?

On Sat 01 Jun 2019 at 08:52:24 +0200, Francesco Messineo wrote:
> thanks! Those are editor ROMs for the CRTC-based PETs, so I didn't
> even try to compare the unknown ROM to them. Who knows why they
> modified one of those to be used on a non-CRTC PET :)

I can't find the document I wrote once upon a time which compared the
various PET ROM versions that I was aware of. But I seem to remember
that the Basic 4 "upgrade" ROM, the one for the machines without CRTC,
did not have 100% the same functionality as the CRTC version.

Things that come to mind are
- some missing screen control characters
- a bug in the numbering of one of those screen control characters (or
  the lack of the bug),
  (aha: http://www.zimmers.net/anonftp/pub/cbm/maps/PETio.txt under the
  header CONTROL CODES)
- different keyboard scan codes in address 151 (pre-4 ROMs used indeed a
  scan code, 4.0 ROMs translated to PETSCII before storing there)
- http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/README
  mentions the lack of a JMP table

I may have missed or misremembered some things, but I can imagine that
somebody would want to create more compatibility by basing an Editor ROM
on the CRTC version. I guess it might even work without modification,
but you may want to remove the writes to the CRTC anyway.

-Olaf.
-- 
___ Olaf 'Rhialto' Seibert  -- "What good is a Ring of Power
\X/ rhialto/at/falu.nl      -- if you're unable...to Speak." - Agent Elrond