Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!edwardj
From: edwardj@microsoft.UUCP (Edward JUNG)
Newsgroups: comp.sys.next
Subject: Re: Optical Disk price change
Message-ID: <58327@microsoft.UUCP>
Date: 18 Oct 90 02:01:12 GMT
References: <72100012@uxh.cso.uiuc.edu> <9198@milton.u.washington.edu> <5774@mace.cc.purdue.edu>
Reply-To: edwardj@microsoft.UUCP (Edward JUNG)
Organization: Microsoft Corp., Redmond WA
Lines: 48

In article <5774@mace.cc.purdue.edu> asd@mace.cc.purdue.edu (Kareth) writes:
>
>Yeah, they are slow, but they continue to get faster, cheaper, and
>larger.  They won't be able to compete against hard drives in speed,
>ever most likely.  But they sure can as for price and volume of
>storage.  And with the amounts of storage people need today, optical
>drives are the ONLY solution for a lot of needs.

Even this is not case in stone.  Today's OD drives have large head 
assemblies that have both emitter/detector and some electronics on
a large, heavy head assembly.  This is similar to the construction
of very early disk hardware.  The high mass of the head results in
a high-profile drive (eg usually full-height for 5.25" drives),
somewhat noisy operation as the head assembly shuttles back and forth,
and relatively slower seek times.

In theory, flat and light optical elements can be constructed that
mount the electronics off the head and conduct light to the detector
and emitter through channels or fibers.  Alternatively, thin film
techniques can product "flat" detectors and emitters.  Some of this
technology already exists (and today's hard disks use it).

The use of such low mass heads would significantly increase the average
access time.  Since OD have dense data, the data rate will always be
high.

The primary defects of OD today are:

  1. writes require a phase change and therefore are slower
  2. single platter may increase time to seek over all data
  3. media is relatively sophisticated when compared to
     floppy disks, which usually deal with a single active
     coating

But as a read media, the media size, seek speed, storage capacity, and
transfer speed can all be made more palatable.

BTW, this is not a response to the "OD are on their way out" message.
I think the thrust of that message was made clear regarding the use
of an open standard.

>BTW, does anybody know if NeXT OD's conform to the ISO standard?

No, they do not conform to the ISO media standard.  I'm pretty certain
that they conform to the ISO form-factor standard, though, so jukebox
media changers would work.

Edward