Re: No PETs allowed demo...

It's probably not really a matter of timing, like some C64/VIC graphic tricks. 
The 6545/6845 CRTC chip is programmable so it's a matter of selecting the proper 
register values. I don't think you need to change them once set. Basically, you 
can adjust the top/left margins, number of characters per line, number of lines, 
as well as the number of pixels high each character is. This is easily done in 
BASIC. Then you can just print or poke to the screen memory.

Not having run the demo myself, I'm guessing the character height is set to 2. 
By creative use of the standard PET character set you could have individual 
control of 2x2 pixel size "points" in a small area.

What would be interesting would be to try this method on an 8296, since it can 
use up to 8K of video ram so you could have a 160x100 pixel graphic mode without 
any additional hardware. With a replacement character generator ROM you could 
thoretically have 640x100 or 320x200.

Steve


----- Original Message ----
> From: Anders Carlsson <anders.carlsson@sfks.se>
> To: cbm-hackers@musoftware.de
> Sent: Wed, December 15, 2010 1:07:37 PM
> Subject: Re: No PETs allowed demo...
> 
> Cameron Kaiser wrote:
> 
> > Still, it's a great mode to leverage if someone can port it to 60Hz PETs.
> 
> In the demo, credits were given to Robin Harbron for testing. Either I am 
>mixing things up, or he owns a 50 Hz (220V European?) PET. Perhaps testing was 
>done at an earlier stage when it was a matter of how the CRTC works at all, not 
>specifically timed for the 4032?
> 
> My last remaining, working PET is named 4032 on the front but as far as I 
>remember it contains a 2001N/3000 series motherboard upgraded with Basic V4. 
>Thus I suppose this demo won't run on my non-CRTC PET.
> 
> However what are the odds the demo would run on a 8032 using one of the 4032 
>emulation programs? I suppose the CRTC registers and timing is so critical it 
>won't work, even if "normal" 40 column software including the (simpler) demo 
>"Hardcore Petting" released earlier this year runs just as well on a 8032 as the 
>intended 4032. I've tried it myself.
> 
> Best regards
> 
> -- Anders Carlsson
> 
> 
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