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From: jmiller@uokvax.UUCP
Newsgroups: net.micro.atari
Subject: Re: Orphaned Response
Message-ID: <38700010@uokvax.UUCP>
Date: Mon, 17-Mar-86 16:45:00 EST
Article-I.D.: uokvax.38700010
Posted: Mon Mar 17 16:45:00 1986
Date-Received: Fri, 21-Mar-86 03:24:23 EST
References: <0@<860306215129>
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Nf-ID: #R:<860306215129:0:uokvax.UUCP:38700010:000:1472
Nf-From: uokvax.UUCP!jmiller    Mar 17 15:45:00 1986


The RGB monitor is no problem since any medium resolution negative sync monitor can be used, however, the monochrome monitor requires a 31.5 KHz
horizontal sweep rate and a vertical sweep rate that can be tweeked
to 71 Hz.  The 71 Hz Vertical sweep was chosen to reduce the

harringbone and barber polling that occurrs because of the internal
frequencies present in the computer required to generate the color
burst sync.  Several monochrome monitors will fit this description
if you are sure that the vertical freq. can be tweeked far enough.
  The monochrome monitor should have a high persistence phosphor
so that flickering will be kept to a minimum.  In monochrome mode,
the video is output in interlaced mode and must scan two complete
frames to complete one picture in the same amount of time that one
frame is scanned in color mode.  Thus the 400 line resolution in
monochrome mode.  There are rgb monitors that can scan at the 35 Khz
rate and have a high persistence phosphor but their cost is around
800.00 plus dollars and that was evidently not considered a
viable option.  This would also require twice as much of aa graphics
frame buffer also causing larger than needed overhead.  The capability
exists within the hardware to do this at a later date whenever the
monitor technology get's to a more economical position.  This would
require different initialization of the graphics crt scan control
registers as well as all the application software routines.