Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cwjcc!ukma!gatech!gt-eedsp!jensen
From: jensen@gt-eedsp.UUCP (P. Allen Jensen)
Newsgroups: comp.sys.mac
Subject: Re: NeXT press release (very long but interesting)
Summary: Technology is feasable, IEEE Article reference
Message-ID: <525@gt-eedsp.UUCP>
Date: 14 Oct 88 14:26:48 GMT
References: <5423@juniper.uucp> <72886@sun.uucp>
Organization: Georgia Institute of Technology
Lines: 41

In article <72886@sun.uucp>, swilson%thetone@Sun.COM (Scott Wilson) writes:
> >   The other VLSI chip, the Optical Storage Processor, controls the
> >256 Megabyte Optical Disk, making possible this new storage technology
> >The Optical Disk combines the vast storage capacities, removability
> >and reliability of laser technology with the fast access and full
> >read/write/erase capabilities of Winchester (magnetic) technology.
> 
> Hmm, this looks suspicious to me.  Note that the the terms "vast
> storage capacities", "removability", and "reliability" are used to
> describe laser technology while "full read/write/erase" capabilites
> are associated with Winchester (magnetic) technology.  ......


The Feb. 1988 issue of the IEEE Spectrum contains an article which should
help clarify some of the questions about the technology.  The article
is "Optical disks become erasable" by Robert P. Freese of Alphatronix, Inc.
Basically, new materials allow the data to be magnetically stored by
heating the disk to arround 150 degrees C and applying a magnetic field.
The reading is done  using a low power beam utilizing the Kerr magneto-optic
effect.  The plane of polarization of the beam will be rotated depending
on the pole orientation.

The article states that drives with 20-ms access time had already
been demonstrated (Feb. 1988).  The article refered to "First Generation"
drives with "40 to 100ms" access times and that "Second-generation"
magneto-optic drives with 20-ms access times had been demonstrated.
The article went on to predict that as the technology developed,
access times would approach and possibly exceed current winchester
technology.

Based on this article, I think that the 96ms seek time is probably
a worst-case and that the 30-ms is probably correct for a peak access
time.  I think that the NeXT claims are probably accurate based on
this article.

P. Allen Jensen
-- 
P. Allen Jensen
Georgia Tech, School of Electrical Engineering, Atlanta, GA  30332-0250
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