Date   : Mon, 19 Feb 1996 13:42:24 GMT
From   : lamcw <lamcw@...>
Subject: Re: Graphics speed hacks

James Fiddell wrote:

;I believe that it should be 20000 ticks at 1MHz -- that is, 1/50th of
;a second.

;How did you come up with the 19990 figure ?

I looked at the user T2 counter figures which Revs pokes into it and
they add up to 19990 ticks. Revs doesn't tie these interrupts to
the vsync one and therefore to keep sync the duration of one frame
must exactly match 19990 ticks. Otherwise the colours scroll very slowly
up/down the screen :)

Elite is much simpler as it uses vsync to split the screen.


Chris Lam,
MacBeebEm Keeper.