samperi@dasys1.UUCP (Dominick Samperi) (10/14/87)
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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