Nice to see that someone managed to hang onto one of these. To offer a bit more information on the "battle of the shirt-pocket floppy", IBM wasn't competing just against the Sony 3.5" format, but also the Dysan/Shugart 3.25" format, which, as is the IBM prototype, more in the 5.25" true "floppy" format.
The field is littered with casualties. Amstrad used the 3.0 inch CF format for a time; Zenith had the "shrunken" 2.5" size....etc. etc. All in all, I think the right format won the battle--3.5" floppies are physically pretty rugged. Not that any of this matters today. :) --Chuck On 08/22/2018 06:28 AM, Eric Schlaepfer via cctalk wrote: > Yesterday I dug out my prototype IBM DemiDiskette drive and took some > photos: https://twitter.com/TubeTimeUS/status/1032066215647166464. It > caused a bit of interest on Twitter so I figured some of you here may also > like seeing it. > > I don't really know a whole lot about it other than what my grandfather > told me (he worked on the team that developed it). Dates on the remaining > paperwork go from December 1979 through August 1980. It was supposed to be > a very low cost drive for the microcomputer market (target price IIRC was > <$100). Although it was originally developed by a team working at IBM > Austin, it was handed off to a different team apparently working out of > Rochester. > > The disk capacity was not very large--I don't remember the exact number but > it was probably around 100K or less. > > A few interesting observations: > > * The stepper motor uses a spiral cam to convert rotation into linear > motion to drive the head. > * It is a single-sided drive. > * A microswitch senses the presence of the disk instead of an optical pair. > * There is no write protect notch or sensor. > * There is no index sensor. > * The spindle drive motor is a DC brushed motor with an encoder wheel for > speed control. > * Not shown in the pics, but the plastic "spot welds" holding the vinyl > jackets on the disks are intentionally widely spaced making the cookie > easier to remove for analysis. > > It's not really something you get to see every day, that's for sure...