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From: rlw@ttardis.UUCP (Ron Wilson)
Newsgroups: comp.sys.apple
Subject: Re: 5.25 floppy disk formats
Message-ID: <2425@ttardis.UUCP>
Date: 11 Jan 90 15:25:02 GMT
Organization: Gallifrey
Lines: 23

In article <9060.infoapple.net@pro-generic>, sb@pro-generic.cts.com (Stephen Brown) writes:
>In-Reply-To: message from paul@athertn.Atherton.COM
>
>[lots of stuff on FM and MFM disk data encoding methods deleted]
>Whatever you say about Apple's proprietary encoding technique, you have got to
>admit it's pretty good. Consider that you get 140K per side, or 280K per
>double-sided disk in single density. That's not too bad in comparison to IBM's
>360K /disk double-density.
>
>sb@pro-generic

Apple did not use a proprietary format per se.  The data encoding technique
Steve Wozniak used was around long before he designed and built the Disk ][
prototype (I don't remember where it was originally developped).

As it happens, the Commadore 1541 disk drive (and some of the other Commadore
disk drives) also use the same encoding technique (I know this because I
once analysed a 1541 formatted disk on my Apple //e with a Disk ][ - actually,
I could only read the inner most tracks of the diskette: the 1541 rotates
the diskette at a constant LINEAR velocity; where as the Disk ][ spins the
disk at a constant angular velicity - this allows the 1541 to store even more
data than the Disk ][ because it can put 22 sectors per track on the outermost
tracks)