Xref: utzoo comp.sys.mac:21906 comp.arch:6769 comp.sys.next:104
Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ames!husc6!encore!gloom!cory
From: cory@gloom.UUCP (Cory Kempf)
Newsgroups: comp.sys.mac,comp.arch,comp.sys.next
Subject: Re: NeXT press release (very long but interesting)
Summary: CD-ROM's use spiral track too
Message-ID: <169@gloom.UUCP>
Date: 20 Oct 88 16:28:45 GMT
References: <5423@juniper.uucp> <72886@sun.uucp> <635@ardent.UUCP> <73226@sun.uucp>
Sender: news@husc6.harvard.edu
Followup-To: comp.sys.next
Organization: Alloy Computer Products, Framingham, Mass.
Lines: 23

In article <73226@sun.uucp>, lyang%scherzo@Sun.COM (Larry Yang) writes:
> An audio CD has as its "format" basically one, long serial spiral
> (not unlike its vinyl counterpart).  In computer applications, I believe
> the disks are usually formatted into wedges (sectors), not unlike its
> magnetic counterpart.  Thus, along with the ECC overhead, there is the
> overhead for formating the sectors, labeling the sectors, etc.

A data CD (at least in the standards that I have used) is formatted
in a LONG spiral.  the spiral is broken down into several blocks,
each of which "looks" like it is 2k.  In reality, they use some
error correction code (ECC) that causes 8 bits to use up 14 bits 
of space.  

A CD-ROM holds about 660Mb of data after ECC, or on the order of
1 Gb without the ECC.

Unfortunately (at least from what I have heard), the Audio CD's (and
CD-ROM's are not compatable with the WORMs or WMRM drives.  The Audio
CD/CD-ROM work on a laser reflection off of pits in the substrate of
the disc.  (NB: when refering to CD's, disc is correct, not disk.)
-- 
Cory Kempf
UUCP: {decvax, bu-cs}!encore!gloom!cory
revised reality... available at a dealer near you.