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Help doc: Document behaviour of video emulation when in full-speed mode #477

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tomcw opened this Issue Aug 20, 2017 · 4 comments

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tomcw commented Aug 20, 2017

Need to document:

  • Full speed mode favours speed over video accuracy
    • Video only updated periodically (once a wall-clock 60Hz frame) instead of each opcode
  • In full speed, timing loops won't work correctly (eg. ANSI Story)
  • In full speed, card detection routines (that rely on floating bus) won't work correctly (eg. Ankh, #474)

Also worth stating how to enter full-speed mode:

  • Implicitly: drive motor on (and enhanced drive mode enabled), etc.
  • Explicitly: ScrollLock key, gg from debugger, etc.

@tomcw tomcw added the Help label Aug 20, 2017

@tomcw tomcw changed the title from Help doc: Document behaviour of NTSC emulation when in full-speed mode to Help doc: Document behaviour of video emulation when in full-speed mode Aug 20, 2017

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tomcw Nov 11, 2017

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Also from #508:

  • In full speed, Apple II+ VBL detection routines won't work (so the code will just hang)
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tomcw commented Nov 11, 2017

Also from #508:

  • In full speed, Apple II+ VBL detection routines won't work (so the code will just hang)

@tomcw tomcw self-assigned this Nov 11, 2017

@tomcw tomcw added this to the 1.27 milestone Nov 11, 2017

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tomcw Dec 13, 2017

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Also from #4:

  • In full speed, Drol didn't work

IIRC there's some video-scanner sync'ing going on in this game, so again won't work with 1.26 in full speed mode.

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tomcw commented Dec 13, 2017

Also from #4:

  • In full speed, Drol didn't work

IIRC there's some video-scanner sync'ing going on in this game, so again won't work with 1.26 in full speed mode.

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sicklittlemonkey commented Dec 13, 2017

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tomcw Dec 16, 2017

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It's a shame it doesn't work at full-speed...

Yes, I agree. It's not the best user experience.

We could have the emulator detect II+ VBL detection, eg:
-LDA $C050
BNE -

This check could be done periodically, eg. at the start of the next batch of 6502 emulation, in CpuExecute().

I'll spin this discussion out into a dedicated issue.

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tomcw commented Dec 16, 2017

It's a shame it doesn't work at full-speed...

Yes, I agree. It's not the best user experience.

We could have the emulator detect II+ VBL detection, eg:
-LDA $C050
BNE -

This check could be done periodically, eg. at the start of the next batch of 6502 emulation, in CpuExecute().

I'll spin this discussion out into a dedicated issue.

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