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From: jbn@wdl1.UUCP
Newsgroups: net.micro
Subject: Re: CD-ROMS
Message-ID: <585@wdl1.UUCP>
Date: Mon, 5-Aug-85 01:30:59 EDT
Article-I.D.: wdl1.585
Posted: Mon Aug  5 01:30:59 1985
Date-Received: Tue, 6-Aug-85 12:22:50 EDT
Sender: notes@wdl1.UUCP
Organization: Ford Aerospace, Western Development Laboratories
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Nf-ID: #R:brl-tgr:-1146700:wdl1:1400058:000:593
Nf-From: wdl1!jbn    Jul 22 14:04:00 1985


     It's not just head movement time.  The grooves on laser disks are closer
together than the positioning accuracy of the read head, or indeed, the
tolerance on position of the center hole of the disk.  Thus, to find a
track, you must move to the right neighborhood and wait until the track ID
information comes around to tell you where you are, then move accordingly and
try again.  If the track ID information only appears on the disk once per
rev, this can take a while, and so it does on the video form of the disk.
But this need not be the case in all-digital formats.

					John Nagle