Path: utzoo!attcan!uunet!microsoft!edwardj
From: edwardj@microsoft.UUCP (Edward JUNG)
Newsgroups: comp.sys.next
Subject: Re: Can NeXT play audio CD's?
Keywords: CD, CD-ROM
Message-ID: <55081@microsoft.UUCP>
Date: 7 Jun 90 00:00:30 GMT
References: <5596@helios.TAMU.EDU>
Reply-To: edwardj@microsoft.UUCP (Edward JUNG)
Organization: Microsoft Corp., Redmond WA
Lines: 79

In article <5596@helios.TAMU.EDU> daugher@cs.tamu.edu (Dr. Walter C. Daugherity) writes:
>Sun Microsystems is now pushing CD-ROM, and has announced in an official news
>release that
>
>	"In 1991, Sun plans to convert exclusively to compact disc as the
>	distribution medium for all its system and application software."
>
>Finally catching up to NeXT, eh?

The issue of CD-ROM vs. MOD (Magneto-Optical Drive) are orthogonal.
CD-ROM is read-only, and a very cost-effective way of distributing
information such as documentation.  You can produce a CD-ROM for as
little as $2.00 per CD (makes you wonder about how much the record
companies are making on CDs), with a fixed cost that ranges from
$2000 to $15000.  This is *much* cheaper than distributing on paper.

On the other hand, NeXT's MOD is read/write, and thus can be used
for backup, secondary storage, and even (shudder) primary storage.
MOD, however, is more expensive.  NeXT's MOD is $50.00 per single-
sided disk.  NeXT's MOD is also NOT ISO standard (like the Sony,
Ricoh and Maxtor systems, which usually work with double-sided
media -- you must flip it to access the other side, and have a
slightly higher storage density).

In both cases you have the added benefit of on-line searching, browsing,
and other tools unavailable when using paper documentation.

As far as speed, there are two factors: access time and transfer rate.
The access time AND transfer rate of CD-ROM are quite slow.  The transfer
rate is fixed by the audio standard (the rate used by the CD audio output
governs the rate of the motor of the drive).  The access time is slow
because the standard CD mechanism doesn't have to be real fast.  The
ISO file system standard is just a way of indexing and retrieving files
on the CD so different OS can access the same CD (they obviously cannot
write their own file system structures on the CD-ROM).

MOD today have relatively fast transfer rates.  Their access times are
usually 3-5 fold worse than hard disks.  This is largely due to the
high mass of the optical heads.  Thin film heads are possible; this would
reduce the access times to equivalent or better than hard disks.  The
gating factor is not technology, but mostly market demand to justify the
cost of development and mass-production.

Finally, bit densities of CDs are higher because they are stamped and
do not allow change.  With MOD, the density is lower due to the fact that
both heat dissapation (with the laser) and magnetic field are involved;
they both are local effects.  Phase change optical disks (e.g. recently
promoted by Panasonic) promise higher densities (as well as compatibility
with WORM -- write-once read-many optical disks).

Summary: CD-ROM: Very cheap, very high density, very slow access and transfer.
   NeXT MOD: Medium cost, high density, medium access time, high transfer rate.
   ISO MOD: High cost, high density, medium to fast access, high transfer rate.
   Removable HD: medium-high cost, low density, fast access, high transfer, medium reliability
   Fixed HD: no media, very high density (low per-platter), very fast access,
         medium to very high transfer rate, medium-high reliability.

>
>	"And yes, you CAN play your CD audio discs in the SunCD! A headset or
>	speakers can be plugged into the audio jack located on the front
>	panel."
>
>Can a NeXT do that?

No.  The NeXT MOD is not a CD player; it can neither read the ISO format
CDs, nor play audio CDs, not CD-I, nor read or write ISO format MOD media,
nor read or write any WORM media.

>
>Walter C. Daugherity
>Texas A&M University
>daugher@cs.tamu.edu (Internet)
>uunet!cs.tamu.edu!daugher (uucp)
>DAUGHER@TAMVENUS (BITNET)


Edward Jung
Systems [Strategic Architect | Architectural Strategist]
Microsoft Corp.