CoCo Floppies: Was:These darned old computers

From: Fred Cisin <>
Date: Wed Aug 28 20:23:00 2002

> > Sure, if you look just inside the dust flap on a 3.5" drive, and you see a
> > switch {or optical sensor) on the right hand side, it's a 1.44Meg - that's
> > the 1.44Meg sense switch to see if it has a HD disk in it. If the switching

On Thu, 29 Aug 2002, Tony Duell wrote:
> Be very careful. Some early 3.5" drives (including the 600 rpm
> full-height Sony units) put the disk-detect sensor on the right. Well, it
> was a logical place to put it, out of the way of the write-protect
> sensor, before there were 1.44M disks. So a sensor on the right need not
> imply a 1.44M drive.

And some of the early 1.4M drives that IBM used had no 1.4M/730K sensor!
It would try both densities in read attempts, and you could
specify in software to write the lower density (for example:
FORMAT A: /T:80/N:9 ), but if you put in a 720K diskette and tried to
format, the drive would have no way to know that it was not a 1.4M.

> Incidentally, such drives often won't work _at all_ with 1.44M disks. The
> HD hole lines up with the disk-detect sensor so the drive thinks there's
> no disk inserted.

At least that way, it never misinterpreted a disk as the WRONG type.
Received on Wed Aug 28 2002 - 20:23:00 BST

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