[net.unix-wizards] VAX 750 reset button makes clock jump back

m.wales@Ucla-Security@sri-unix (12/11/82)

From: m.wales at Ucla-Security (Rich Wales)
Date: 8 December 1982 1145-PST (Wednesday)
We are running 4.1BSD on several VAX 750's.  On most of them (maybe
all, but I'm not sure), if you reboot by hitting the white RESET
button, the time-of-day register sometimes loses several minutes
(usually about five minutes).  The same thing happens if you power off
and then power on.

The problem doesn't seem to be dependent on UNIX.  I walked up to a
750 just now that had been running DEC diagnostics, and I was able to
produce the problem in console mode.  (The command "E/I 1B" below dis-
plays the TODR register -- the clock.)

	    >>>E/I 1B
		I   0000001B   8A501304
	    >>>
	    [I hit the RESET button here.]
	    %%
	    00000000  16
	    >>>E/I 1B
		I   0000001B   8A4F248C		<-- NOTE: jumped back!
	    >>>

The funny thing is that, when I subsequently tried the same thing on
the same machine, the problem would not recur.  Perhaps it is something
which will only happen once every several hours on a given CPU.  Since
the problem is not reliably reproducible, I don't know whether it
affects all our 750's or just some of them, and so far we have not been
able to get a satisfactory solution from DEC.

Has anyone out there encountered this problem?  Has anyone been able to
get DEC to fix it?

-- Rich Wales (Wales at UCLA-Security)