Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!amdahl!oliveb!cygnet!mark
From: mark@cygnet.CYGNETSYSTEMS (Mark Quattrocchi)
Newsgroups: comp.ivideodisc
Subject: Re: CD (roms) question
Message-ID: <691@cygnet.CYGNETSYSTEMS>
Date: 14 Jan 88 21:47:21 GMT
References: <7813@eddie.MIT.EDU> <1988Jan10.214104.7965@gpu.utcs.toronto.edu>
Reply-To: mark@cygnet.UUCP (Mark Quattrocchi)
Organization: Cygnet Systems -- Sunnyvale, CA
Lines: 30

In article <1988Jan10.214104.7965@gpu.utcs.toronto.edu> nishri@gpu.utcs.UUCP (Alex Nishri) writes:
>
>>What exactly is the capacity of a standard size CD, both in bytes and
>>in playing time for music (assuming a standard speed)?
>
>CD-A can have up to 72 minutes of audio, but due to molding problems toward the
>outer edge of the disc, it is rare to see 60 minutes exceeded.  (The 'audio' is
>actually in a spiral track which goes from the inside to the outside.)
>
>CD-ROM, which uses the same disc, track, speed and other physical specifications
>can store approximately 550 megabytes of data.  The actual amount quoted in
>various sources varies both because the term 'megabytes' is not standard (is
>it 1000000 bytes, or 1000 times 1024 bytes or is it 1024 times 1024 bytes?) and
>because the amount of data you can store depends on the amount of error
>correcting & detecting overhead you have.  If you are interested in the
>technical details "CD-ROM Review" has covered them.  A good book to read is
>the 1987 Bradley CD-ROM book.  Incidently, CD-ROM is one sided because CD-A
>is.  CD-ROM gets its economies of scale by using the same glass mastering and
>the same disc pressing plants as does CD-A.
>
>Larger discs using the same technology are more expensive because they don't
>enjoy the economies of scale.  A large optical disc can have one gigabyte worth
>of data on one side.  There do exist two sided versions with two gigabytes worth
>of information.
>
And if you want even higher capacity you can buy one of our jukeboxes which
can hold up to 242 gigabyes.


>There also exists something called optical tape.  The same kind of technology
>is used on a tape surface.  Capacity is measured in hundreds of gigabytes ...