Re: P500

Hi Ullrich,
 
You got your reply in while I was writing... nice. And thanks for the disassembly listing!
 
Someone definitely needs to fix that kernal ;-)
Steve


>________________________________
> From: Ullrich von Bassewitz <uz@musoftware.de>
>To: cbm-hackers@musoftware.de 
>Sent: Tuesday, November 6, 2012 4:40:51 PM
>Subject: Re: P500
>  
>
>Hi!
>
>On Tue, Nov 06, 2012 at 10:15:04PM +0100, Christian Dirks wrote:
>> The screen scrolling seems very slow to me.
>> Since I haven't seen a working P500 before, I don't know, if it is
>> alwas that slow.
>                                                          
>Scrolling (and video output in general) is slow on the P500. Commodore seems
>to have had issues with accessing the VIC and the video/color RAM, so they
>used rather complex write routines. See the routines wrtvic, wrtvram and
>wrtcram in the ROM listing:
>
>http://www.von-bassewitz.de/uz/oldcomputers/p500/rom500.s.html#AALV
>
>Fortunately the routines to write the RAM are called via vectors:
>
>http://www.von-bassewitz.de/uz/oldcomputers/p500/rom500.s.html#AAL5
>
>Since most versions of the P500 don't have the access problems, one can change
>the write vectors to point to simple write routines instead of the complex
>original ones. This will speedup the output considerately.
>
>> The ROMs are -02's.
>
>These are the latest ROMs known to exist. At least to me:-)
>
>Regards
>
>
>        Uz
>
>
>-- 
>Ullrich von Bassewitz                                  uz@musoftware.de
>
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>
>
>   

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