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baslinux - Re: [BL] Re: What's an optical (MO) drive?

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  • From: "Anthony J. Albert" <albert AT polaris.umpi.maine.edu>
  • To: baslinux AT lists.ibiblio.org
  • Subject: Re: [BL] Re: What's an optical (MO) drive?
  • Date: Tue, 18 May 2004 10:44:13 -0400

On 17 May 2004 at 20:10, Sindi Keesan wrote:
>My partner has heard of these MO disks and says they came out about the
>same time as the 1.44M floppy disks. He did not realize they were such
>high capacity. Are they Bernoulli, he asks. Stiff or floppy? What he
>heard of is 3.5" size, is this? They sound pretty clever.

I think they were a little behind the 1.44MB floppy. While the
Bernoulli also came out about the same time, it's not the same thing at
all.

Bernoulli and ZIP drives are very similar - both are optically-tracked
hard drives. There are optical guide marks, laid down at the factory,
to guide what is essentially a hard drive head & disk into alignment.

Magneto-Optical drives are read only with a laser... much like a CD-
ROM. The read laser passes through a protective plastic layer, then an
active dye layer, then reflects off a silvered layer. The laser
reflects back, with a slight phase change in the light - this change is
used to detect the state of the bit, either "on" or "off".

When writing an MO, it takes a laser & a magnetic head, with the laser
heating up the dye, and then the magnetic head changing state of that
little spot of dye from one state to another.

Here's a longer and more detailled explanation:
http://www.usbyte.com/common/MOsystems.htm

MO comes in a variety of styles and formats, but the earliest ones were
single-sided 5.25" disks, which held 256MB or so - when many hard
drives were the same size! They quickly progressed to the 512MB and
1GB sizes, which were fairly common, then to 2GB.

Also, 3.5" formats were introduced, holding smaller amounts of data per
disk, but costing less for the drive, and weighing a lot less. My old
5.25" 1GB unit is pretty heavy!

Finally, they've come out with greater capacities. Sony and others
make some 5.2GB and 9.1GB 5.25" units now... they're priced about about
US$1000 per drive, and the media are about US$12 per GB of capacity.

Here's a link to a picture of the media
http://www.business-supply.com/dept/2107619/verbatim-5-1-4-optical-
diskettes.html

Overall, they're handy and useful, but the expense limits them to niche
markets, and you may see them phased out in favor of rewriteable DVD
over the next few years.

Hope this helps,
Anthony Albert
===========================================================
Anthony J. Albert albert AT umpi.maine.edu
Systems and Software Support Specialist Postmaster
Computer Services - University of Maine, Presque Isle
"This is only temporary, unless it works."
--- Red Green





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