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one cycle

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  one cycle mmphosis <mmphosis@macgui.com> - 2017-04-01 16:46 +0000
    Re: one cycle TomCh <tomcharlesworth26@gmail.com> - 2017-04-02 07:42 -0700
      Re: one cycle mmphosis <mmphosis@macgui.com> - 2017-04-02 17:53 +0000
        Re: one cycle Zellyn <zellyn@gmail.com> - 2017-04-02 12:14 -0700

#3406 — one cycle

http://hoop-la.ca/apple2/2017/onecycle/

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#3408

On Saturday, April 1, 2017 at 5:49:46 PM UTC+1, mmphosis wrote:
> http://hoop-la.ca/apple2/2017/onecycle/

AppleWin only does an I/O address check and floating bus read on the opcode fetch, not the opcode's parameter byte(s).

So only the access to $C056 will work as expected, not the subsequent reads from $C057 and $C058 (they will not change video mode, and will just read 0x00 data). So the code will jmp $0000.

Tom

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#3409

Awesome!  Thanks for the info Tom.  Now I know why some of my code was doing
what it was doing on AppleWin.  I am hoping to explore this a little
further: executing code that is (or may be) on the floating bus.  I really
wish I had real hardware.

Thanks again. :)

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#3410

Ooh! I've been thinking of this, mainly in the context of antagonizing 4am :-)

I *think* OpenEmulator does the floating bus correctly, at least on II and II+, but I hope to write comprehensive emulator tests for this soonish...

Zellyn

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