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Path: utzoo!watmath!clyde!rutgers!ames!ptsfa!pbhyd!lc
From: lc@pbhyd.UUCP
Newsgroups: comp.sys.apple
Subject: Re: On hi-res character generation
Message-ID: <836@pbhyd.UUCP>
Date: Thu, 19-Feb-87 13:20:38 EST
Article-I.D.: pbhyd.836
Posted: Thu Feb 19 13:20:38 1987
Date-Received: Fri, 20-Feb-87 21:34:41 EST
References: <394@thumper.UUCP>
Reply-To: lc@pbhyd.UUCP (Larry Colton)
Organization: Pacific * Bell, San Ramon, CA
Lines: 18

In article <394@thumper.UUCP> sdh@thumper.UUCP (Retief of the CDT) writes:
>
>Just a simple point, that it is fact very easy to do scrolling
>for a hires character generator that is just as fast as normal
>test scrolling.  The way to do this is to write a program that
>builds a scroll routine.  

I presume the author of the above meant to say hi-res screens
could be made to scroll as fast as *text* screens.  Not hardly.
Each line of text on a text screen requires one line of screen
memory (40 bytes).  Each 'text' line on a hi-res screen requires 8 
lines of screen memory (320 bytes).  Since a memory move routine does
not care what memory is being moved, it should be obvious that the
best a hi-res scroll can do is 8 times slower than text scroll.

Some other factors will impact this (80 column text, use of look
up tables instead of bascalc, etc) but in no case will hi-res 
scrolling ever be as fast as text screen scrolling.