Path: utzoo!mnetor!uunet!husc6!think!bloom-beacon!mit-eddie!uw-beaver!cornell!batcomputer!braner
From: braner@batcomputer.tn.cornell.edu (braner)
Newsgroups: comp.sys.atari.st
Subject: Re: ST hardware scrolling
Message-ID: <4484@batcomputer.tn.cornell.edu>
Date: 20 Apr 88 16:06:35 GMT
References: <544@csvax.liv.ac.uk>
Reply-To: braner@tcgould.tn.cornell.edu (braner)
Organization: Cornell Theory Center, Cornell University, Ithaca NY
Lines: 24
Summary: yes and no

[]

Two problems with the suggestion for "hardware scrolling":

(1)  The ST's video pointer must be on a 512-byte boundary, NOT 256.
Thus, incrementing it by $500 (1280) (to scroll by one text line)
is NOT feasible.  (I tried it: the screen goes crazy!)  One could
scroll TWO text lines at a time, though.

(2)  This solution only applies to scrolling the entire screen,
while Tempus, Laser C, etc fast-scroll arbitrary WINDOWS.  Rather
impressive.

What I do in MORE.TTP for fast scrolling is: no scrolling.  I clear
the screen before writing the next one.  That is a lot faster since,
again, 32000 bytes need to be manipulated (cleared, in this case)
only once per 25 lines.  It is also faster in another sense:  The
user can glance at the top lines while the bottom ones are being
printed.  In MORE (and GNOME too!), if you see that you want to scroll
further, you press the appropriate key and the printing of the current
screen is aborted immediately, the screen is cleared, and the next
screen is printed.

- Moshe Braner