3b1 tape drives

DoN Nichols dnichols at ceilidh.beartrack.com
Thu May 16 10:09:30 AEST 1991

In article <1991May13.231146.4710 at com50.c2s.mn.org> caa at com50.c2s.mn.org (Charles Anderson) writes:
>I was talking to a friend of mine the other day and he made a comment about
>having a couple of floppy tape drives lying around since no one was using
>them, and I was wondering if anyone knew any specifics on plugging one of
>these suckers into my machine....I don't really care if I have to replace
>the floppy drive (It sucks anyways.)  Is it possible???  Has it been done?

	Yes, it is possible.  It has been done (by Convergent Technoligies),
but it requires a extra card containing a second floppy disk controller.
Find someone in your area who has the Technical Reference Manual and look at
the section on the floppy tape drive.  The schematics of the controller are
shown.  (I don't remember whether it involves any undocumented PAL chips.)

	The drive used is exactly the same as that used for the 3b2, and is
a full-height drive, so you can't just swap out your floppy drive, even
assuming that you could make the driver use the floppy-disk's interface, and
that there is nothing extra needed.  If I remember, the drive-select lines
are used to select which track the drive will use, so there is a bit of
interface difference between the tape drive and the floppy.  I don't think
the hardware mods are practical even if you had a modified kernel with the
necessary driver.  You need a loadable device driver with the interface.

	Given the minuses of the floppy tape drive, if you can't find one
with controller and software, you would be better off investigating another
angle.  The floppy-tapes MUST be formatted FROM A DIAGNOSTIC DISK, hold only
23MB on a DC-600A cartridge (which should hold 60MB otherwise), and are
painfully slow.  I find it quicker to tar to remsh (with the ethernet) to
another system with a SCSI drive, and pipe that through dd into the drive.
Same tape cartridge, 60MB, faster, and NO PRE-FORMATTING!

	Also, you need to keep the floppy drive for rebuilding the system
after a crash :-)

	We can keep hoping that someone will complete the scsi interface, so
we can hang such a drive directly on our own system.  (I'm lucky having a
mix of systems connected by ethernet.)

	Good Luck
Donald Nichols (DoN.)		| Voice (Days):	(703) 664-1585
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