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From: banksie@whitu.isor.vuw.ac.nz (Philip Banks)
Newsgroups: comp.sys.acorn
Subject: Re: MODE 21 & MULTISYNC
Message-ID: <1991Jan06.013149.22420@comp.vuw.ac.nz>
Date: 6 Jan 91 01:31:49 GMT
References: <1990Dec21.031201.3334@odin.diku.dk> <1990Dec21.101354.1261@urz.unibas.ch>
Sender: news@comp.vuw.ac.nz (News Admin)
Reply-To: banksie@whitu.isor.vuw.ac.nz (Philip Banks)
Organization: Dept. of Comp. Sci., Victoria Uni. of Wellington, New Zealand.
Lines: 46
Nntp-Posting-Host: whitu.isor.vuw.ac.nz

In article <1990Dec21.101354.1261@urz.unibas.ch>, gaspar@urz.unibas.ch writes:
|>In article <1990Dec21.031201.3334@odin.diku.dk>, seifert@freja.diku.dk
(Michael Seifert) writes:
|>> Hi All,
|>> 
|>> I have a problem with Mode 21 and a multisync monitor. My machine is
|>> configured 
|>> as follows:
|>>   Arc 410/1
|>>   2Mb Ram, 20Mb HD, 3.5" floppy disk-drive.
|>>   Eizo 9060SZ MultiSync Monitor
|>> 
|>> The problem:
|>>   When I access the (floppy) diskdrive in mode 21, my screen will
turn "black
|>>   with a small gray border" several times. It seems to me the it goes black
|>>   whenever information is read from the diskdrive.
|>
|>I think it is a completely normal behaviour, although very strange!
|>I have the same hardware and see the same effects.
|>Maybe it's the problem that there cannot be so much data (320K 50 times a
|>second) be brought from memory to the screen and at the same time a
lot of data
|>from the disk to memory.
|>
	  And indeed that is percisely the case. From my experience any screen 
   mode with more than about 220k of screen memory will blank out when
the floppy
   drive is accessed. You will notice that the hard drive does not cause this 
   problem and this is due to timing factors. With a floppy drive you have long
   start rotation times and a slower rotation speed so that for fast
disk access
   the computer *must* be ready to accept the data whenever it arrives. However
   with a hard drive the high rotation speed (and the disk cacheing on
some of the
   drive controllers...) skipping a rotation is not so serious in terms
of speed
   and the Arc can accept the data at its own pace. Thus the screen does not
   blank out!
	  Here endeth the explanation.
                               
*-----------------------------------------------------------------*   @@@@@@/|
|   BANKSie! (aka Philip Banks) banksie@isor.vuw.ac.nz            |   @@@@@/#| 
|      An Arc owner stuck in a non Arc spot.                      |   @@@@/##|
|  Well you try drawing the Arc Symbol in Ascii 'Graphics'!       |   @@@/---|
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