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From: mangler@cit-vax.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: software density select with tc13 & fuji 2444-ac
Message-ID: <2019@cit-vax.Caltech.Edu>
Date: Thu, 12-Mar-87 02:18:57 EST
Article-I.D.: cit-vax.2019
Posted: Thu Mar 12 02:18:57 1987
Date-Received: Fri, 13-Mar-87 04:39:52 EST
References: <43125@beno.seismo.CSS.GOV>
Organization: California Institute of Technology
Lines: 28
Summary: density select sometimes a speed select

In article <43125@beno.seismo.CSS.GOV>, rick@seismo.CSS.GOV (Rick Adams) writes:
> A scope on the density select pin out of the controller shows that the
> line never goes high to indicate hi density.

Some streamers, such as the CDC 92185, abuse the density select line to
select high speed or low.  The TC13 caters to this, asserting the line
when the drive seems to be streaming well.  (You didn't see it asserted
because the program wasn't fast enough to stream the tape, probably).

To use that line as a density select, you have to enable the "Remote
Density Select" DIP switch (SW3-8), and I think you also have to set
the transport type switch (SW1-4) to "Formatted" instead of "Streaming".

When you try this with a CDC 92185 (see above), any time you try to
select high density, the drive will go into high-speed streaming mode,
rocking the tape back and forth.  I never did figure out how to get
the 92185 to interpret that signal as a density select instead of a
speed select.  (If anyone does, let me know...)

Oh yes, the manual says this wasn't implemented until Rev. C; but
Rev. B didn't work at all with the 4.2 BSD distribution tape, so
I assume that's not your problem.  (Only the low 8 bits of the
cmd/msg buffer pointer would increment, and the generic kernel
put it right across a page boundary.  I gave Emulex a listing of
VAX console examine/deposit commands to demonstrate it - if you
want a hardware vendor to fix something, that really grabs them).

Don Speck   speck@vlsi.caltech.edu  {seismo,rutgers,ames}!cit-vax!speck