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Path: utzoo!linus!philabs!seismo!hao!cires!nbires!milo!zhahai
From: zhahai@milo.UUCP
Newsgroups: net.micro.pc
Subject: flicker free scrolling
Message-ID: <144@milo.UUCP>
Date: Wed, 21-Dec-83 18:06:10 EST
Article-I.D.: milo.144
Posted: Wed Dec 21 18:06:10 1983
Date-Received: Fri, 23-Dec-83 04:36:13 EST
Organization: NBI, Boulder
Lines: 23

Thanks for the information about the USI board.  I am wondering, however, what
flicker-free scrolling really is?  Does that mean that the screen doesn't have
hash on it while the processor accesses video ram (ie: correctly dual ported,
probably by carefully time synchronizing the two accesses to avoid conflicts)?
Or does it scroll by moving the initial pointer into video ram which is used
to refresh the display (eg: add new data after last line of screen data, change
the first line displayed)?  Or, finally, by some on-board memory to memory mover
which is faster or better synchronized than 8088 accesses?  Can anyone help
any on this?  The ads are not very clear on this, and the salepeople and
support folks I have spoken with so far were not credible.  Is there more than
one "flicker-free scrolling" technique?

Also, is the flicker free scrolling for all modes?  Character and graphics,
monochrome and color?

Thanks for your input.  I will try to get a look at a USI board (now from 
Universal Research according to another respondent ???).
		Zhahai Stewart (at NBI Inc)
-- 

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