Groups > comp.sys.apple2.programmer > #6023

Re: Vertical Blank on Apple ][+

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From	mmphosis <mmphosis@macgui.com>
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Subject	Re: Vertical Blank on Apple ][+
Date	Thu, 23 Mar 2023 14:33:12 -0000 (UTC)
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> Does this work on both hi-res screens?

For HGR2, change the $2000 addresses to $4000 addresses and BIT $C055 before
the wait routine.

> And on a IIe with the $C019 soft switch, Instead of racing the beam (or
> staying ahead of the refresh), isn't it better to start drawing when the
> beam is finished refreshing and is at the bottom of the screen, about to
> go
> up, and start drawing to the screen then.  Doesn't this do the same thing
> but offers a little more time to draw to the screen before the screen gets
> updated on the next time around?

Timing is everything and is fraught with peril.

http://www.deater.net/weave/vmwprod/megademo/cycle_switching.html

https://rich12345.tripod.com/aiivideo/softalk.html

https://web.archive.org/web/20150706084550/http://hoop-la.ca/apple2/2015/winterwarmup/

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Re: Vertical Blank on Apple ][+ Dave Kay <thavith@gmail.com> - 2023-03-16 03:35 -0700
  Re: Vertical Blank on Apple ][+ Michael Pohoreski <michael.pohoreski@gmail.com> - 2023-03-21 08:59 -0700
    Re: Vertical Blank on Apple ][+ I am Rob <gids.rs@sasktel.net> - 2023-03-21 15:32 -0700
      Re: Vertical Blank on Apple ][+ mmphosis <mmphosis@macgui.com> - 2023-03-23 14:33 +0000

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