First 3.5 inch FDD [WAS: RE: Prototype IBM DemiDiskette drive]

[Chuck Guzis]

On 08/23/2018 11:43 AM, Tom Gardner via cctalk wrote:
> Well it all depends upon what u mean by "first"
> 
> The Sony drive and cartridge were not compatible in many ways with what
> became the physical, magnetic and electrical interface standards for the
> 3.5-inch drive and cartridge.  The standards came out of the "Microfloppy
> Industry Committee" (Google it with quotes) organized by Shugart Corp.
> Either Shugart or Tandon was the first to ship drives compatible to the
> standard.  Tandon probably did the first such cartridge.

I must confess some bewilderment.   Around 1981, I did some contract
work for an outfit called Preis for their portable computer.  I don't
recall the nature of the work anymore, but I still have a copy of their
BIOS for CP/M.

At any rate, the thing used the Sony 0A-D30 single-sided 600 RPM
floppies, which held about half as much as the corresponding 8" media
(in FM, about 160KB). The major differences were that the Sony drive
could access only 70 cylinders, while the 8" drives could do 77.  In
addition, the Sony spun at 600 RPM, which allowed for the use of an 8"
drive interface, albeit at a reduced track capacity over the 8" drive.

One other notable aspect was that the Sony's 26-pin interface had no
motor control line--the disk spun continuously, just like its 8"
relatives.  Similarly, it had a head-load solenoid, just like the 8"
drives.

Media-wise, I believe there was little difference between the Sony
floppies and more modern DS2D commodity media.  I believe the disk
shutters were not sprung, but were manual.

I used to have a couple of these drives, but scrapped them because the
modern slow 3.5" drives did a better job of handling floppies.

Where Shugart fits into all of this, I have no idea.

--Chuck