I always though it was an awesome idea, but no one ever copied it. Even if more complicated than a standard eject mechanism, I guess it should not have been so outrageously expensive not to be considered by anyone else except Apple?


So, as people pointed out in the comments, the very idea of automatic ejection could not have been patented, only actual implementations. However, could have it instead been that what was patented was the software implementation/idea that by locking a floppy disk in the drive data integrity can be more easily enforced (let's ignore software bugs in the OS) without requiring the filesystem to do journaling or employ other performance-killing data integrity techniques?

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    I'd imagine it was patented, but there were other systems with mechanical disk ejection — Sun workstations for example. – Stephen Kitt Oct 1 '16 at 17:09
  • Could the very idea of mechanical ejection be patented at all? – user180940 Oct 1 '16 at 17:21
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    @user180940, a specific ejection mechanism could be patented; the fundamental idea of "automatically eject a floppy" can't. – Mark Oct 1 '16 at 19:21
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    @user180940 And, related to your "awesome idea" statement: You have apparently never faced a disk stuck in a soft-eject drive that wouldn't eject. In situations like that, you might reconsider the "awesome" ;) – tofro Oct 2 '16 at 10:27
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    Also copied on some workstations, for example SparcStations, to enforce safe 'unmounting'. – TEMLIB Oct 2 '16 at 19:13

Yes, the mechanical mechanism was patented. I can't find any evidence for a software patent.

It looks to be US patent 4466033 which was originally developed for the Lisa's Twiggy drive but adapted for use in the original Mac drive. Here is a quote from the second link:

The Sony 3.5” micro-floppy was uniquely enhanced for the Macintosh by incorporating performance, capacity and data integrity improvements which had been prototyped with a 5.25" floppy by way of five innovations [...] Fifth, the software-controlled floppy clamping and eject mechanism [Ref-3: '033 patent] - a signature characteristic of the Macintosh - insured file system integrity upon ejection of the floppy disk. The one-chip controller in combination with these five innovations created a fast, high capacity, reliable and low-cost storage device that was unique to the Macintosh. The Macintosh micro-floppy is also discussed on pp. 32, 39-42, 54 and 66-68 of the February 1984 issue of Byte magazine

Here is a quote from the February 1984 issue of Byte magazine, page 39:

In addition to the change to 80 tpi, Apple contracted Sony to modify the drive in several other ways. Two changes allow the Sony drive to mimic the behavior of the Lisa "twiggy" drives (which were originally chosen for use in the Mac): disk ejection under software control and variable disk-rotation speed. The first change allows the Mac to ensure that a disk is correctly updated before it is surrendered to the user (that is, you can't take a disk out of the drive until the Mac software permits it).

Andy Hertzfeld also corroborates Apple working closely with Sony on the drive in this story, and a later Sony patent filed in 1988 cites the original Apple patent.

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    Are you answering to the original question or to the hypothesis I wrote in the edited section ? – user180940 Oct 5 '16 at 3:39
  • The title of the question. I've updated my answer to clarify. – Nick Westgate Oct 5 '16 at 3:58
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    I have referred to that patent in my comment above - The drawings clearly indicate a 5 1/4" drive, so it could be related to the Lisa, but no way to the Macintosh. – tofro Oct 5 '16 at 11:19
  • I've added more on the relationship between the Twiggy and Sony drives. – Nick Westgate Oct 5 '16 at 20:07

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