Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.brl.mil (Doug Gwyn)
Newsgroups: comp.sys.apple2
Subject: Re: More extended graphics on the IIgs
Message-ID: <14923@smoke.brl.mil>
Date: 21 Jan 91 22:17:51 GMT
References: <1991Jan18.170510.1@gacvx1.gac.edu> <14908@smoke.brl.mil> <1991Jan20.123430.7039@ee.rochester.edu>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 11

In article <1991Jan20.123430.7039@ee.rochester.edu> seah@ee.rochester.edu (David Seah) writes:
>Not having a VOC myself, what is it about this board that messes up
>3200 color demos?

Basically, in order to synchronize with an external video source, it
provides a duplicate IIGS video subsystem that is not synchronized to
the one on the motherboard.  Unfortunately the existing 3200-color
demos use the motherboard clock-based signals to coordinate their
updates of scan-line control bytes during the painting of the image.
The effect is that the VOC is using the wrong SCB information since
it is updated out of sync with the VOC scanning.