VBlank synchronisation under AmigaOS 4.x

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68k system friendly games that work under OS4 may be too fast, generating for example screen flickering.

What is the correct way to synchronize them? (this would be done by patching the game in memory or directly)

Thanks

Kamelito

  • TenLeftFingers
    Added tags display, hardware and os4.x
  • Laurent Giroud
    In my humble opinion, this question is way too broad for any answer to be of interest. It would probably be better to ask dedicated questions for games you are interested in.
  • kamelito
    I’m thinking of Cinemaware games especially DOTC. Kamelito
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Have you got a particular game in mind? Any I can think of don’t have any problems, but it’s likely that games that aren’t coded well will have issues. Synchronising to the video frame is something that all games should do to avoid flicker, and it’s been a part of the OS since the very beginning, all the way up to and including OS4. If games do that, they should work perfectly fine without flicker on OS4 too, and instead of running much faster, they’ll spend more time “sleeping” between frames. If a game doesn’t use these vertical blanks for synchronising, then you might have problems but you would most likely also have similar problems with faster classic machines too, such as 68060-based Amigas.

Patching-wise, you could always try inserting a vertical blank wait into the main game loop, but it might introduce strange side-effects if the game was specifically written without them. But really it should already be put there by the game coder in the first place.

  • kamelito
    All 68k games that are system friendly. I guess they should be forward compatible, since they use systems call and not banging the HW. Kamelito
  • Daedalus
    I mean, any game that doesn’t work? From my experience most work very well as they use standard video blank timing.
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