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New game in the works...

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  • uhtred_of_bebbanberg
    Hello, everyone. I just joined this group after stumbling onto MattMik s site. Recently I dusted off my old VIP and am in the process of getting it set up
    Message 1 of 2 , Feb 1, 2011
      Hello, everyone. I just joined this group after stumbling onto MattMik's site. Recently I dusted off my old VIP and am in the process of getting it set up again. Back in high school I wrote several games for various machines, and in my senior year I started a game on the Commodore PET but didn't have time to finish it.

      Now's the time! I'm going to finish up the game on my VIP, and to do that I need to be able to display at least one shade of gray. I have a plain-vanilla VIP, with no expansion boards, so at first I thought I was out of luck trying to display anything other than black or white.

      But as I was reviewing the VIP documentation, I came up with the idea of modifying the standard 64x32 display interrupt routine to use two pages of RAM as even-odd field buffers. Black pixels are off in both buffers; white pixels are on in both buffers, and gray pixels would be on in one buffer but off in the other. The display interrupt would flip back and forth between the two field buffers, and with 60 fields fields per second, gray pixels would be "refreshed" at 30 Hz.

      Has anybody tried anything like this before? I didn't find anything about this technique in any of the online VIPERs. It seems like it would work well for games, but I have no idea what kind of results this technique would produce with emulators.

      If anyone has any thoughts on this, I'd appreciate it. Also, does anyone here run actual VIP hardware, or does everyone just go with emulators?

      Thanks!
    • dddiceman
      ... That s a cool idea, and it should work on the hardware. It probably won t work on an emulator, because the display hardware on the emulating computer will
      Message 2 of 2 , Jul 27, 2011
        --- In rcacosmac@yahoogroups.com, "uhtred_of_bebbanberg" <uhtred_of_bebbanberg@...> wrote:
        >
        > Hello, everyone. I just joined this group after stumbling onto MattMik's site. Recently I dusted off my old VIP and am in the process of getting it set up again. Back in high school I wrote several games for various machines, and in my senior year I started a game on the Commodore PET but didn't have time to finish it.
        >
        > Now's the time! I'm going to finish up the game on my VIP, and to do that I need to be able to display at least one shade of gray. I have a plain-vanilla VIP, with no expansion boards, so at first I thought I was out of luck trying to display anything other than black or white.
        >
        > But as I was reviewing the VIP documentation, I came up with the idea of modifying the standard 64x32 display interrupt routine to use two pages of RAM as even-odd field buffers. Black pixels are off in both buffers; white pixels are on in both buffers, and gray pixels would be on in one buffer but off in the other. The display interrupt would flip back and forth between the two field buffers, and with 60 fields fields per second, gray pixels would be "refreshed" at 30 Hz.
        >
        > Has anybody tried anything like this before? I didn't find anything about this technique in any of the online VIPERs. It seems like it would work well for games, but I have no idea what kind of results this technique would produce with emulators.
        >
        > If anyone has any thoughts on this, I'd appreciate it. Also, does anyone here run actual VIP hardware, or does everyone just go with emulators?
        >
        > Thanks!
        >

        That's a cool idea, and it should work on the hardware. It probably won't work on an emulator, because the display hardware on the emulating computer will likely have its own screen refresh rate (V sync), even if the emulator updates its display using the correct timing. So it would probably generate a "beat frequency" that would display as visible flashing.
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