Re: My ColourPET Project

From: Rhialto <>
Date: Tue, 16 Apr 2013 01:20:12 +0200
Message-ID: <>
On Mon 15 Apr 2013 at 11:25:35 -0700, Steve Gray wrote:
> I am currently disassembling and commenting both 40 and 80 column
> roms, but I don't have a lot of experience with the DIN roms. I think
> there is extra code in there. 
> Which ROM did you try to modify?
> It seems the following are issues to watch out for:
> - CRTC vs NON-CRTC (not much of an issue now)
> - 9" vs 12" Monitor Size- Screen standard (NTSC / PAL / Custom)

9" would all be without CRTC, I think. Unless somebody swapped a new
board into an old case.

>   > First PET had NTSC, rest seem to have custom (ie: 20kHz)
> - 40 / 80 column:
>    > screen line linking
>    > screen line address table
>    > default character set (text / graphics)
> - Keyboard Tables (N / B / DIN / Custom)

Somebody already mentioned that there are different rules about which
keys may be shifted with the Business keyboard (in general, the Normal
keyboard allows shifting on all keys and adds 128).

Some versions of the Editor ROM don't have the jump table at the start.
IIRC these would be the pre-basic-4 ones, and the basic 4 upgrade for
non-CRTC machines. My notes say (I happened across them recently) that
despite the lack of a jump table, many routines actually start in the
same location (as what? that it didn't say) so that *not* using the jump
table would actually be more compatible across versions.

___ Olaf 'Rhialto' Seibert  -- The Doctor: No, 'eureka' is Greek for
\X/ rhialto/at/    -- 'this bath is too hot.'

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Received on 2013-04-16 00:00:03

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