5.24-inch FDD invention [was RE: Diskette size]

Tom Gardner t.gardner at computer.org
Fri Jul 21 22:30:10 CDT 2017

Jobs had nothing to do with the invention of the 5.25" FDD: 

The original impetus for a smaller less expensive FD came from Lanier via Jimmy Adkisson in mid 1975

By early 1976 the Shugart Associate's engineers were working on a medium and device based upon the size of the cassette tape drive

Circa early Feb 1976 Don Massaro and Adkisson visited Wang Labs and Dr. Wang accepted the concept.  This was the key acceptance since at the time Wang was the dominant OEM buyer of FDs.

Feb 22-25, 1976, George Sollman did an East Coast market survey of potential minifloppy users.  The specs presented at that point were essentially the same as the SA400 (I have a copy of the Sollman presentation)

Development test was in June and completed in July; evaluation units went to Wang in August and production units shipped in Sept 1976

A nine month schedule in part due to the use of the 8-inch head which in turn limited the unit to 35 tracks.  The industry ultimately adopted 40 tracks which I think was pioneered by Tandon.

Apple was founded in April 1976 and incorporated in January 1977; the Apple ][ was announced in April 1977 without an FD.  The Disk II did not go on sale until 1978 - two plus years after the SA400 objectives were final.  Clearly Jobs had nothing to do with the invention of the 5.25-inch 

Jobs probably did get his $100 FD by buying a naked drive and allowing Wozniak to do the electronics.  Some observers think the Wozniak design was an innovation and some think it was a disaster, but that is another discussion :-)


-----Original Message-----
From: Chuck Guzis [mailto:cclist at sydex.com] 
Sent: Thursday, July 20, 2017 11:47 PM
To: Steve Malikoff via cctalk
Subject: Re: Diskette size

On 07/20/2017 10:42 PM, Steve Malikoff via cctalk wrote:
> Eric said:
>> I think Shugart settled on 5.25" for the size of a minifloppy at 
>> least a year, and more likely two years, before Steve Jobs would have 
>> visited. I don't have proof, but SA400 public intro was in 1976, and 
>> they probably took more than a year of development to get to that point.
> For interest there's an SA-400 announcement article on page 86 of BYTE, December 1976:
> https://archive.org/details/byte-magazine-1976-12

Others followed quickly.  I think Micropolis was sampling their 100 tpi drive in 1977 according to my memory.  The first ones were pretty buggy, with an ugly tendency to wrinkle the annulus of the diskette.
Apparently they weren't the only ones, as Dysan started to add a reinforcing ring to their 5.25 floppies.  Micropolis eventually solved the problem by detecting when the drive door was being closed and running the spindle motor until the door was fully closed.


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