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

[Tom Gardner]

As Chuck notes the shutter closing was different, the RPM was different and the interface was quite different.  Also different was the media coercivity, media thickness, data rate and physical drive form factor.  Enough differences such that the Sony 0A-D30 drive and medium could not interchange with what became the industry standard for 3½ FDDs and FDs.

What became the standard in all these areas and others was defined by the "Microfloppy Industry Committee" which was formed and led by folks from Shugart Corp.  At its peak it had at least 23 members.  In January 1983 Sony agreed to supply media comporting to the MIC standard.  Both Tandon and Shugart showed drives at Comdex 1982; who shipped first in 1983 is unknown.

Tom 

-----Original Message-----
From: Chuck Guzis [mailto:cclist at sydex.com] 
Sent: Thursday, August 23, 2018 12:20 PM
To: Tom Gardner via cctalk
Subject: Re: First 3.5 inch FDD [WAS: RE: Prototype IBM DemiDiskette drive]

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