*BSD News Article 59104


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From: aflundi@mdl.sandia.gov (Alan F Lundin)
Subject: Why do disk transfers lockup my machine?
Message-ID: <1996Jan9.160757.19783@mdl.sandia.gov>
Reply-To: aflundi@sandia.gov (Alan F Lundin)
Organization: MDL, Sandia National Labs., Albuquerque, NM
Date: Tue, 9 Jan 1996 16:07:57 GMT
Lines: 30

Hi Guys,

I have a quick question.  I have a machine at home that
has a ISA bus motherboard and a 1542B SCSI controller
that locks up while I do disk operations, but returns
to normal afterword.  For instance, I decided to look
at the xperimnt stuff and did

	$ gzcat xperimnt.tgz | tar xvf -

which worked feverishly away, displaying the tar output
in the window I kicked it off in.  However, the other processes
(window manager, xterms, shells, etc.) just couldn't get their
share of the CPU.  The mouse cursor, for instance, would move
only every several minutes, one movement at a time. So as a result,
the machine was unusable while the gzcat/untar command was
executing.

However, I tried the same things on my machine at work which
has a Bt445S SCSI controller on a VLB motherboard without
any similar lockup.  In both cases, I wrote to a directory
on the same disk I read from, and in both cases I was running
2.1R.

Is there something funny about the 1542B controller that causes
this?

--alan
-- 
Alan Lundin <aflundi@sandia.gov>