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From: info-vax@ucbvax.ARPA
Newsgroups: fa.info-vax
Subject: Re: Dual ported TU78s
Message-ID: <5170@ucbvax.ARPA>
Date: Fri, 1-Mar-85 20:32:35 EST
Article-I.D.: ucbvax.5170
Posted: Fri Mar  1 20:32:35 1985
Date-Received: Sat, 2-Mar-85 04:29:06 EST
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Organization: University of California at Berkeley
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From: nbush%sitvxa.BITNET@WISCVM.ARPA(Nicholas Bush)

While the port A and port B positions of the thumbwheel are very nice in
keeping one system from using the drive, DEC's distributed TFDRIVER gets
a little confused about such things.  The drive returns an interrupt
code of "NOT AVAIL" if a system tries to access the tape drive when
it is locked out.  TFDRIVER considers this to be a FATAL DRIVE ERROR.
Since the MOUNT command attempts to access the drive to mount a tape,
you tend to get errors on the system which is locked out.  (Note that
you only get the NOT AVAIL interrupt code when the tape drive is
actually online, but your port is locked out.)  This caused us
much grief when we first ran into it.  I sent in an SPR and
got a "not supported" answer, even though the mods to TFDRIVER are
minimal.

- Nick Bush
  Stevens Institute of Technology