Re: My ColourPET Project

From: Steve Gray <>
Date: Mon, 15 Apr 2013 17:19:10 -0700 (PDT)
Message-ID: <>
So far I have found these hardcoded jumps to the edit rom that do not go through the jump table:
Pasting from my disassembly...
;-------------- Output to Screen (Called from CHROUT in KERNAL)
;               ***** THIS ENTRY POINT MUST NOT MOVE!!! *****
;-------------- Main IRQ Entry Point (Called from KERNAL vector at $FFFE !!!!)
;               ***** THIS ENTRY POINT MUST NOT MOVE!!! *****



> From: Rhialto <>
>Sent: Monday, April 15, 2013 7:20:12 PM
>Subject: Re: My ColourPET Project
>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 01:00:27

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