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From: jim@cs.strath.ac.uk (Jim Reid)
Newsgroups: comp.unix.wizards
Subject: Re: SI 9900 hangs
Message-ID: <670@stracs.cs.strath.ac.uk>
Date: Thu, 20-Aug-87 09:30:04 EDT
Article-I.D.: stracs.670
Posted: Thu Aug 20 09:30:04 1987
Date-Received: Sat, 22-Aug-87 18:18:42 EDT
References: <8269@brl-adm.ARPA> <3321@cit-vax.Caltech.Edu> <654@stracs.cs.strath.ac.uk> <331@cogen.UUCP>
Reply-To: jim@cs.strath.ac.uk
Organization: Comp. Sci. Dept., Strathclyde Univ., Scotland.
Lines: 30

In article <331@cogen.UUCP> alen@cogen.UUCP (Alen Shapiro) writes:
>At Turing Institute Glasgow we had 2 Vax 750s and 2 SI9900s. We frequently
>(couple of times a month) had the aforementioned problem. Without fail, hitting
>the reset button worked. We had our mains monitored and the hangs corresponded
>with voltage spikes/dropouts not severe enough to take down our
>750s but bad enough to cause the 9900s to act like Rip-Van-Winkle

This is the crux of problem. The 9900 power supply is susceptible to
spikes/dropouts in the mains supply. The controller detects the loss of
its DC power and forces the drives to do an "off-spindle" seek. [The
reasoning being if the power has gone (or just about to go), it would
be better to retract the heads in case they parked in the middle of the
disk.] Then when the DC power comes back a few moments later, the
controller can't recover causing someone to manually flick the
reset switch.

I'll talk to our SI repairpersons and post a detailed explanation soon.

>I seem to remember SI installed a driver fix that could detect when the problem
>occured and did an off-spindle* seek to reset the drive.

Strange. I've never heard of this "driver fix". It does sound a bit of a
kludge, though I suppose getting the kernel to poke the controller would
probably work if SI couldn't make the power supply work correctly.

>ps Hi Jim

Hi Alen - We'd better stop meeting like this!

		Jim