Baslinux mailing list

["Anthony J. Albert" <albert AT polaris.umpi.maine.edu>]

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