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From: samperi@dasys1.UUCP (Dominick Samperi)
Newsgroups: comp.sys.ibm.pc,comp.sys.att
Subject: cpio for DOS and 3b2 - followup
Message-ID: <1647@dasys1.UUCP>
Date: Wed, 14-Oct-87 14:28:14 EDT
Article-I.D.: dasys1.1647
Posted: Wed Oct 14 14:28:14 1987
Date-Received: Fri, 16-Oct-87 21:37:34 EDT
Organization: The Big Electric Cat, NYC, NY
Lines: 48
Keywords: cpio, floppy, DOS, 3b2
Xref: mnetor comp.sys.ibm.pc:9074 comp.sys.att:1495

A while back I posted a request for information on the AT&T 3B2 floppy
drive, so that I could find a way to do file transfers between IBM PC's
and 3B2's via floppy disks. My aim is to write a version of cpio for
IBM PC's running MS-DOS that can read/write floppy cpio archives in IBM PC
or 3B2 format. It already has the capability of writing archives that
are compatible with the format used by Microport's System V/AT and
SCO Xenix. 

The only remaining problem is to determine how to read/write individual
sectors on a DS/DD floppy in 720K format (see 1 below). I know that there
is a program (intrcpt) that enables one to do this with DOS 3.2, but I'm
interested in a solution for DOS 3.* (I'm using 3.1). Perhaps someone
can give me a few pointers to tech journal articles on this. Apparently,
the program Fastback has the capability of writing 720K floppies with
DOS 3.1, so it is possible. I only need to read/write sectors; there's no
need for higher-level 720K floppy I/O.

Here is a summary of the information I've received so far,
and of my tests:

1. The 3B2 floppy drive formats 360K floppies so that they can store
   720K bytes by writing 80 tracks/side, two sides, with 9 sectors/track.
   Since there are 512 bytes/sector, the total capacity is 737280 bytes.

2. Standard IBM PC 360K drives write only 40 tracks/side, yielding a
   total capacity of 368640 bytes.

3. cpio archives can be written to 360K floppies in 3B2 (720K) format by
   using special device files supplied with Microport's System V/AT
   (/dev/rdsk/fd096ds9), or SCO Xenix (/dev/rfd096ds9). This is done 
   using a high density (1.2 Meg) drive on an AT.

4. Some of the responses included the suggestion that high density floppies
   be used, for increased reliability, but I haven't been able to do this
   on the AT's that I tested.

5. I haven't been able to transfer multi-floppy cpio archives between 
   the AT UNIX systems I tested and a 3B2.

6. At the present time my cpio for DOS can be used to transfer multi-floppy
   cpio archives between DOS and either of the AT UNIX systems mentioned
   above.

-- 
	Dominick Samperi, Manhattan College, New York, NY
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