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From: gnu@hoptoad.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: tar (really brain damaged tape controllers)
Message-ID: <2213@hoptoad.uucp>
Date: Fri, 29-May-87 02:14:00 EDT
Article-I.D.: hoptoad.2213
Posted: Fri May 29 02:14:00 1987
Date-Received: Sat, 30-May-87 08:04:10 EDT
References: <1003@bobkat.UUCP> <926@nrcvax.UUCP> <697@hao.UCAR.EDU>
Organization: Nebula Consultants in San Francisco
Lines: 30

In article <697@hao.UCAR.EDU>, woods@hao.UCAR.EDU (Greg Woods) writes:
>   We have such an Integrated Solutions machine, and the swapping option is
> quite nice for writing VAX-compatible tapes (our users are used to VAX byte
> order and receive many such tapes in the mail for analysis). Of course, 
> since I.S. allows you to have the byte swapping done in the device driver
> (by using /dev/srmt0 instead of /dev/rmt0, etc.), we just switched the device
> names around to make VAX byte order the default for tapes. It works great.

Ho ho!  There is no such thing as "VAX byte order on tapes".  There is
just "correct byte order on tapes".  The standards for 1600 bpi tapes
were defined by IBM years and years ago, and the bytes are in a very
certain order.  E.g. if you write (hex) 0001020304050607 to a tape, the
bytes come out 00, then 01, then 02, etc.  Never 01, 00, 03, 02, ...
It sounds like Integrated Solutions ships their systems with "incorrect
byte order on tapes" as the default, and then claims that the ability
to fix it is a feature.

One will get you five that they are using a Tapemaster tape controller,
like Plexus, the other system known to have this bug.  At least they
provide the swap option in the driver; Plexus makes you do it with dd,
and doesn't document that it isn't compatible with anybody else's
systems.  On reasonable systems using the Tapemaster, of course, the
"swap option in the driver" is not an option, it's always on.  You can
cry about the performance loss, but "I can make it arbitrarily fast, if
you'll accept the wrong answer!"

-- 
Copyright 1987 John Gilmore; you may redistribute only if your recipients may.
(This is an effort to bend Stargate to work with Usenet, not against it.)
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