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From: dillon@POSTGRES.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga.tech
Subject: Re: State of PD system enhancement (was: Two Amigas)
Message-ID: <8909191954.AA00396@postgres.Berkeley.EDU>
Date: 19 Sep 89 19:54:44 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 21

:in article <34.filbo@gorn.santa-cruz.ca.us>, filbo@gorn.santa-cruz.ca.us (Bela Lubkin) says:
:> X-Claimer: I >am< R Pentomino!
:
:> What happens if you Forbid() as the block starts, can you get away with
:> cycle counting? 
:
:Dave Haynie Commodore-Amiga Writes: (daveh@cbmvax.commodore.com)
:One big problem is that you never know exactly how long it'll take to write
:to the CIA chip.  It's hooked into the system via the 68000's 6800 family
:support mechanism.  The CIA runs from a clock that's 6 68000 clocks low,
:4 clocks high.  When you access the CIA, the 68000 will synchronize to this 
:free running 716kHz clock; depending on where the 68000 cycle is in relation
:to the CIA cycle, this can sync-up can vary quite a bit.  So handshaking 
:between machines is a requirement.

	Oh, THAT is why the cycles weren't comming out!  I'm getting
    28KBytes/sec out of the thing which is 35uS/byte and I just couldn't
    figure out why it was taking so long!  Now it's obvious, I only
    access the CIA in just about every instruction!

					-Matt