Path: utzoo!mnetor!uunet!husc6!uwvax!oddjob!gargoyle!ihnp4!cbosgd!clyde!watmath!watdragon!daford
From: daford@watdragon.waterloo.edu (Daniel Ford)
Newsgroups: comp.ivideodisc
Subject: Re: CD-ROM
Message-ID: <4481@watdragon.waterloo.edu>
Date: 5 Jan 88 02:25:12 GMT
References: <19898@teknowledge-vaxc.ARPA> <4469@watdragon.waterloo.edu> <2132@bloom-beacon.MIT.EDU>
Reply-To: daford@watdragon.waterloo.edu (Daniel Ford)
Organization: U. of Waterloo, Ontario
Lines: 39


In article <2132@bloom-beacon.MIT.EDU> yba@athena.mit.edu (Mark H Levine) writes:
>In article <4469@watdragon.waterloo.edu> daford@watdragon.waterloo.edu (Daniel Ford) writes:
>>As I understand it, CD ROM discs in their current form could not be
>>double sided.
>This seems unnecessarily pessimistic on several counts:
>
>Music CDs which use the same basic technology + a D/A converter come double
>sided, CD-ROM drives can mechanically accomodate these disks as far as I have
>seen (they use the same bloody drive in the case of Hitachi product I was
>shown, and the only restriction on WORM product was the form factors involved).
>The labelling problem is somewaht silly -- two-sided music cds have labels on
>both sides, as do 8, 10, and 12 inch optical disks for video (with 2 sides).
>The lasers do not seem to have any trouble with the plastic coat, nor would
>I expect any.




I may be displaying my ignorance, but as far as I know music CD's do NOT
come double sided.  They may look double sided because one can see the
silver through the transparent top side, but they are not.  Also, I don't see
how one could expect a laser to penetrate an optically opaque label and read
the data stored on the disk surface below.  This seems doubly strange since
the manual for the above mentioned Hitachi drive warns that if the 
disk surface is fogged by condenstation the drive is likely to have problems 
reading data.




					Dan Ford


-- 
---------------------------------------------------------------------
Daniel A. Ford 					daford@watdragon.uucp
CS Department                         daford%watdragon@waterloo.csnet
U. of Waterloo       daford%watdragon%waterloo.csnet@csnet-relay.arpa