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From: rsfinn@athena.mit.edu (Russell S. Finn)
Newsgroups: comp.sys.mac.programmer
Subject: Re: alternate screen buffer on Mac II
Keywords: alternate screen buffer, Mac II, VIA register
Message-ID: <1990Mar15.222250.7763@athena.mit.edu>
Date: 15 Mar 90 22:22:50 GMT
References: <1990Mar13.040203.6874@Neon.Stanford.EDU> <16691@well.sf.ca.us>
Sender: news@athena.mit.edu (News system)
Reply-To: rsfinn@athena.mit.edu (Russell S. Finn)
Organization: Massachusetts Institute of Technology
Lines: 24

In article <16691@well.sf.ca.us>, brecher@well.sf.ca.us (Steve Brecher) writes:
> 
> In article <1990Mar13.040203.6874@Neon.Stanford.EDU>,
> carter@Neon.Stanford.EDU (Thomas J. Carter) writes:
> 
> > ...I'm having trouble finding the alternate screen buffer on a Mac II
> > with a combination of monitors.  Can this be done?
> 
> No.  An alternate screen buffer is not a feature of Mac II video.

Now, far be it for me to contradict one of the Big Names of the
Macintosh Community, but it *is* possible to do page flipping on (at
least) a standard Apple Video Card.  The problems are that it's not
documented very clearly; it's a function of the video card, not the main
hardware; you have to make calls directly to the video driver (i.e., you
can't just flip a bit in the VIA); and it's not recommended by Apple. 
However, if you're really game, it's possible.  You have to go digging
in the Apple "Designing Cards and Drivers for the SE and II" book, and
look in the chapter on video drivers; the information is there.  (Sorry
I can't be more specific, as I don't own this book, or a Mac II; but I
*have* seen it done.  It should work on any third-party video card that
supports *all* the standard video driver calls; apparently, few of them do.)

-- Russ