Re: What is UniDisk ?

[spec@vax2.concordia.ca (Mitchell Spector)]

In article "Benjamin Summers" <summersb@ucs.orst.edu> writes...

>The Unidisk 5.25 was Apple's replacement for the venerable Disk II.  It
>featured an updated design, was tan in color, had a DB-19 cable and a
>daisy-chain port on the back to which other drives could be connected.  The
>drive was later changed in color to platinum and rechristened the Apple 5.25
>Drive.  The Duodisk, a contemporary to the Unidisk 5.25, was basically two
>Unidisk drives in the same casing which was as wide as the Apple IIe console
>and designed to sit on top.

    Another feature worth pointing out was the UniDisk 5.25 was designed
as a half-height floppy drive, encased in plastic (its predecessor, the
Disk II, was a full-height drive with a metal side casing). Basically it
and the Apple 5.25 were more streamlined versions of the Disk II.

>The Unidisk 3.5 was Apple's first 3.5" drive for the Apple II line.  Like
>the Unidisk 5.25, it had the DB-19 cable and daisy chain port on back. (The
>Unidisk 3.5 was later dropped in favor of the Apple Disk 3.5, a different
>design, at the time of the launch of the IIgs).

    Actually there was a prototype "DuoDisk 3.5", which like the DuoDisk
5.25, would have been a single unit with two floppy drives inside. You
can see an image of one on Tony Diaz's page (http://www.apple2.org).

    One important difference you forgot to mention: The UniDisk 3.5 was
an "intelligent" drive, whereas the Apple 3.5 was a "dumb" drive. There
was a specialized circuit board inside the UniDisk 3.5 drive which had
its own processor, memory, IWM controller and firmware. This was needed
for the IIc, in order for the drive to process data before sending it
on to the machine (which was too slow to do the job by itself). You
can easily spot a UniDisk 3.5 as it matched the snow-white color of
the IIc and had its access LED and eject button ABOVE the disk insert
slot (the Apple 3.5 has them in-line).

Mitchell Spector
spec@vax2.concordia.ca