Yes, the CRTC register values are set only once. I was actually thinking of extending the screen beyond 1kB, because that leaves quite little pixel data. So I thought of copying/rewriting the screen data while the CRTC draws them on the screen. But a quick calculation of memory copying speed with 6502 told me that it would rather not be possible. Regards, Michau. W dniu 2010-12-15 20:27, Steve Gray pisze: > 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 <firstname.lastname@example.org> >> To: email@example.com >> 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 >> >> >> Message was sent through the cbm-hackers mailing list >> > > Message was sent through the cbm-hackers mailing list > Message was sent through the cbm-hackers mailing listReceived on 2010-12-15 22:00:14
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