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Groups > comp.sys.apple2.programmer > #3023

Re: Vertical Blank on Apple ][+

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> Has anyone determined what size of area can be drawn within a vertical
> blank period?

4550 cycles = 65 cycles * 70 lines, from:

http://rich12345.tripod.com/aiivideo/vbl.html

And, 4550 cycles is just the VBL period, you can get more cycles (17030
total) by "racing the beam" as others have mentioned -- and that's at 60
frames per second!

As, for how much screen area can be painted in 4550 cycles?

Coding for speed:

1137.5 bytes = 4550 / 4 cycle STA absolute instruction

That's painting more than the entire GR, GR2, TEXT or TEXT2 screen with the
same byte.  Or, you could paint over an eight of the hi-res screen with the
same byte.

I think an interesting thing to do would be to flip the graphics modes while
racing the beam:

https://www.youtube.com/watch?v=KD6ocf_0Bkw

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Vertical Blank on Apple ][+ Norman Davie <ecompservices@gmail.com> - 2016-08-22 15:26 -0700
  Re: Vertical Blank on Apple ][+ John Brooks <jbrooks@blueshiftinc.com> - 2016-08-22 16:47 -0700
  Re: Vertical Blank on Apple ][+ roger.shimada@gmail.com - 2016-08-22 17:48 -0700
    Re: Vertical Blank on Apple ][+ mmphosis <mmphosis@macgui.com> - 2016-08-23 02:30 +0000
      Re: Vertical Blank on Apple ][+ Michael J. Mahon <mjmahon@aol.com> - 2016-08-22 22:06 -0500
      Re: Vertical Blank on Apple ][+ "Mark D. Overholser" <marko@markoverholser.com> - 2016-08-23 07:57 -0700
      Re: Vertical Blank on Apple ][+ roger.shimada@gmail.com - 2016-08-23 17:55 -0700
        Re: Vertical Blank on Apple ][+ Michael J. Mahon <mjmahon@aol.com> - 2016-08-23 21:52 -0500
          Re: Vertical Blank on Apple ][+ John Brooks <jbrooks@blueshiftinc.com> - 2016-08-23 20:44 -0700
            Re: Vertical Blank on Apple ][+ Mark Lemmert <mark.lemmert@gmail.com> - 2016-08-23 22:49 -0700
              Re: Vertical Blank on Apple ][+ zellyn@gmail.com - 2016-08-24 07:15 -0700
                Re: Vertical Blank on Apple ][+ Mark Lemmert <mark.lemmert@gmail.com> - 2016-08-24 19:59 -0700
              Re: Vertical Blank on Apple ][+ Michael J. Mahon <mjmahon@aol.com> - 2016-08-24 11:57 -0500
                Re: Vertical Blank on Apple ][+ Mark Lemmert <mark.lemmert@gmail.com> - 2016-08-24 20:00 -0700
                Re: Vertical Blank on Apple ][+ "Mark D. Overholser" <marko@markoverholser.com> - 2016-08-24 23:32 -0700
                Re: Vertical Blank on Apple ][+ Michael J. Mahon <mjmahon@aol.com> - 2016-08-25 20:51 -0500
                Re: Vertical Blank on Apple ][+ Michael J. Mahon <mjmahon@aol.com> - 2016-08-25 20:51 -0500
                Re: Vertical Blank on Apple ][+ gids.rs@sasktel.net - 2016-08-25 21:41 -0700
                Re: Vertical Blank on Apple ][+ mmphosis <mmphosis@macgui.com> - 2016-08-26 18:52 +0000
                Re: Vertical Blank on Apple ][+ Mark Lemmert <mark.lemmert@gmail.com> - 2016-08-26 06:47 -0700
            Re: Vertical Blank on Apple ][+ roger.shimada@gmail.com - 2016-08-28 08:33 -0700
  Re: Vertical Blank on Apple ][+ olivier.zardini@itn-group.eu - 2016-08-25 09:18 -0700
    Re: Vertical Blank on Apple ][+ Michael Pohoreski <michael.pohoreski@gmail.com> - 2016-08-28 14:58 -0700
      Re: Vertical Blank on Apple ][+ Norman Davie <ecompservices@gmail.com> - 2016-08-28 16:19 -0700
        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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