Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!blars!blarson
From: blarson@blars
Newsgroups: comp.os.os9
Subject: Re: OS-9 disk formats
Message-ID: <184@blars>
Date: 1 Apr 91 23:33:10 GMT
References: <1991Mar28.214614.21461@athena.mit.edu>
Sender: news@usc
Reply-To: blarson@usc.edu
Lines: 64
Nntp-Posting-Host: dianne.usc.edu
Originator: blarson@dianne.usc.edu

In article <1991Mar28.214614.21461@athena.mit.edu> consi@athena.mit.edu (Thomas R Consi) writes:
>Could someone list all the various OS-9 floppy disk formats for both
>5.25 and 3.5 inch floppy disks?

5.25 and 3.5 inch floppy drives are are signal compatable, so the same formats
work on both, although the most common may vary.

(Warning: I'm omiting "hi-density" formats since I'm not familiar with them.)

Pick and choose:

single or double sided

35, 40 or 80 tracks/side

single or double density track 0 side 0, or ignore it completely

single or double density rest of disk

sectors numbered starting at 0 or 1

sector size: 256 (512 possible on some systems)

sectors/track: 10 (single density) 16 or 18 double density

interleave only affects the speed of access, not the ability to
access, so we don't have to worry about it here.



Some of these are hardware dependant, but a good "720k" drive will be
able to read any of the above with a decent controler, driver, and the
proper descriptor.  If the first sector of the disk can be read, you
can find out what format the rest of the disk is in, and a good driver
will use that information.

An unfortunatly large number of the possible combinations of the above
are used in practice.  It can take a while to figure out a "os9" disk
of unknown format.

Some common combinations:

track 0 single density, rest of disk double density (16 sectors/track).
sector offset 0. ("microware")

entire disk double density, 18 sectors/track, sector offset 1 ("coco")

>Which of these formats would be accessible to a Color Computer 2 running
>OS-9 level I ver. 2.00 with the SDisk device driver and 5.25 and 3.5
>inch floppy drives?

Most of them, I think, but you would have to put together the
descriptors.  "universal"(ly-detested) format that skips track 0
completely may not be.  (It is a relitivly new invention of
Microware's, apperently designed to make everybody hate it.)

-- 
blarson@usc.edu
		C news and rn for os9/68k!
-- 
Bob Larson (blars)	blarson@usc.edu			usc!blarson
	Hiding differences does not make them go away.
	Accepting differences makes them unimportant.