RFC: Floppy reader/writer project (recovering UniPlus Unix for the Lisa)

[Chuck Guzis]

On 21 Feb 2008 at 15:40, Jules Richardson wrote:

> Would a non-contact head 'fly' properly at floppy speeds, though? (I'm not 
> sure how much more rotational speed you could get out of a floppy, even 
> jacketless - I suspect the media is just too flexible)

Isn't the Bernoulli drive a non-contact system?  IIRC, the media is 
about the same flexibility as a standard floppy disk.  And 4x speed 
drives were used routinely in duplication equipment, so I don't know 
what the upper speed limit is, but 1200 RPM should be workable.
 
> Would magnasee work usefully at floppy bit densities? I thought it was mainly 
> intended to detect track-level problems and large areas of damage, but could 
> easily be wrong there.

Floppy recording is done at about 5876 BPI for 360K 5.25" and 17,434 
BPI for 1.44MB 3.5".  You can get developer in very fine (10 nm) 
particle size.  See, for example:  

http://www.sigma-hc.co.jp/english/media.html

> Someone elsewhere came up with the concept of 'scanning' a floppy surface in 
> some kind of flat-bed scanner device (and then post-processing to convert X-Y 
> motion into rotational). I don't think there's any practical way of doing that 
> right now, but maybe one day. There's a nice advantage in that the media 
> itself (the critical, fragile bit!) doesn't have to actually move in any way.

I think they've been available for awhile:

http://www.tristantech.com/pdf/SMM-401_v0.2.pdf

Serious bucks, though.

Cheers,
Chuck