Re: C64 BASIC V7 compatibility

From: silverdr_at_wfmh.org.pl
Date: Sat, 29 Jun 2013 14:18:09 +0200
Message-Id: <4EF7FBDF-BC22-4E2A-8190-9CCDC5EC4FB3@wfmh.org.pl>
On 2013-06-29, at 13:58, Ruud@Baltissen.org wrote:

> Building a V7 version for the C64 and VIC-20 I surely will loose 
> compatibility. My goal is that V2 programs should run without any 
> problem. ML programs is another question. 
> 
> The vectors starting from $FF81 on should be maintained. But what 
> about the rest? IMHO I should draw a line at $E37B for the C64 
> ($E378 for the VIC-20): below you only find BASIC routines, above 
> only C64/VIC-20 dependent routines. (that is, AFAIK) 
> So programs using routines like 'Clear screen' at $E544 should run 
> fine but programs using routines in the BASIC area will certainly 
> crash after my changes.
> 
> I have thought about removing the RS-232 and tape routines as well 
> but having loads of KBs at my disposal, I decide to keep them. And 
> if I want JiffyDOS or another speed loader onboard, again: room 
> enough!
> 
> Any comment, idea or suggestion on the above is welcome!

I'd say - obviously - the KERNAL vector table must be preserved. If you can keep the most typical entry points like $e544 or $ab1e or similar - great, but if keeping them would impede the port being done, then they are not worth keeping. OTOH you said there is plenty of room and if you run out of it, then there are still tape and RS-232 routines to be removed. This means you can possibly always keep the most common entry points without problems. The most difficult part is probably to compile a reliable list of such points for various machines..

-- 
SD!


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Received on 2013-06-29 13:00:04

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