TU-58's under VAX UNIX

[obrien%rand-unix at sri-unix.UUCP]

From:  Michael_OBrien <obrien at rand-unix>

	I did some specialized work to get the console cassette interface
on VAX-11/750's into a useable state.  The thing goes right into the CPU
via a special, char-at-a-time interface that defaults to 19.2Kbaud.  VMS
can handle this, UNIX can't (except sometimes when UNIX is single-user).

	I'm an old so-and-so who can't stand owning a device I can't use,
so I complained until someone led me to a PROM sitting in the middle of
the street which, when used in the TU-58, implemented a byte-at-a-time
acknowledgement (called MRSP) instead of the packet-level acknowledgement
seen under standard RSP.  MRSP only takes place if you initialize the thing
with a special flag on in the command packet, otherwise it behaves like
an old RSP PROM, so all the DEC stuff still works.

	If you do this, the driver in 4.2 can be convinced (via
#define MRSP) to talk this protocol.  730's already have MRSP installed
in them.  The chip I found was not a 730 chip; it seems to be some
intermediate version.  No, I can't supply copies.  Don't ask.  I think if
you duplicate the PROM in a 730's TU-58 and plug it into a 750's TU-58
it should work just fine.  No guarantees.

	Some of the stuff in the 4.2 TU-58 driver is mine, like the new
minor device that does write-with-read-verify, some error handling, etc.
Basically it's not really a useful device except for those (like Berkeley,
whom I really had in mind when I did the work) who have to do bootable
distributions.  Also old so-and-so's like myself who can't stand to own
unusable devices.  Now, if anyone has a 4.1 or 4.2 version of a driver
for TU-56 DECtape I, I'd like to hear from you...