4 floppy disk drives on a PC?

From: Fred Cisin <cisin_at_xenosoft.com>
Date: Sun Jan 16 18:56:51 2005

On Sun, 16 Jan 2005, Vintage Computer Festival wrote:
> The whole impetus behind this was that I was trying to read an old 360K
> (might even be 320K or even 180K, I'm not sure) disk and while I could
> read the directory, none of the files larger than say a cluster could be
> read. I attributed this to the drive not being a "true" 360K drive.

Are you sure that the disk is in a PC-DOS format?
If the diskette is 96tpi (720k 5.25) such as PC-JX, Toshiba 300, . . .
then track 0 will be readbale, but the other tracks won't.

if the boot sector, and/or the first byte of the FAT is wrong/different,
then DOS will misunderstand the disk parameters and screw up.

> Fred seems to be the Guru with regards to floppy formats, and perhaps I
> misinterpreted what I read, but I recall him bringing up a scenario in
> which a disk formatted as 360K on a newer drive would not be readable on
> an "actual" (i.e older) 360K drive, or the other way around, or something.

The most common problem is that 96tpi drives, both 720K and 1.2M, write a
narrower track than 360K (about 1/6 mm wide at about 1/4mm center to
center, v about 1/3mm wide at about 1/2mm center to center)
Because of that, when a 96tpi drive REWRITES a track that was previously
written by a 48tpi drive, it might not reliably erase all of the edges of
the old track. In such a case, it should still read reliably in a 96tpi
drive, but not necessarily reliably in a 48tpi. OR,... if you format a
VIRGIN (or bulk erased) disk as 360 in a 1.2, it should read OK.

Grumpy Ol' Fred     		cisin_at_xenosoft.com
Received on Sun Jan 16 2005 - 18:56:51 GMT

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