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From: wieser@cs-sun-fsd.cpsc.ucalgary.ca (Bernhard Wieser)
Newsgroups: comp.sys.mac.programmer
Subject: si Video wierdness
Message-ID: <1990Dec20.172543.26392@cpsc.ucalgary.ca>
Date: 20 Dec 90 17:25:43 GMT
Distribution: na
Organization: U. of Calgary Computer Science
Lines: 24
Nntp-Posting-Host: cs-sun-fsd


Greetings;

	I do lots 'o nifty experiments using various Macintosh for the
psychology department here which require smooth 'animation'.  How I
do it is pregenerated all my 'frames' in advance before I blast them
onto the screen (sometimes using copybits).  Sometimes I use icons,
since IM says (if I remember correctly) they work on a low level (i.e.
ignoring window stuff and some QD; just a basic bytethrower).
I draw my stuff, then wait for a slot vertical retrace interrupt from
the video board.  This has effectively removed flicker on our IIxs,
cxs, IIs, (my SE30), etc...  BUT I just recently ran one of this
experiments on an si...  My timing checks came back and told me I
didn't miss an irq, however the image flickered miserably!
Could it be that using main memory for video memory with the built in
board slows it down sooo much?  Contention for the cpu?  Comments
from anyone who also uses 1 vbl irq to drive drawing are appreciated.
If you've tried your stuff on the si, does it flicker?

-- 
(    Bernie Wieser, wieser@cpsc.ucalgary.ca, BSWieser@uncamult.BITNET    )
(    4rth Year Dbl.Mgr Cpsc Clhc University of Calgary     |             )
(    S/H Developer Dept. of Psychology, "   "   "         \|/            )
(    Octavian Micro Development Group                  --- o ---         )