Jumping R/T clock

[P.E.Smee at gdr.bath.ac.uk]

We're having problems with the real-time clock on a SPARCserver 330 (SunOS
4).  Basically, every so often it slips by an (apparently) randomish
amount of time.  After losing a couple seconds a day all last week (which
I could live with) it decided on Monday night to suddenly set itself back
by an hour and 13 minutes.  Anyone else seen anything like this?  Any
ideas where to start looking?  It doesn't happen often enough for us to
have detected a pattern yet.

Things we *think* we have checked and eliminated (unless we're being
hacked by someone clever enough to clean up their tracks):

1) Doesn't appear to be due to power outages.  (The supply is a notionally
   clean UPS anyway.)

2) Access on 'date' and relatives looks good; no unaccounted uses of
   'date' in lastcomm.  Similarly, no reboots at a time which could explain
   it.  No unaccounted-for logins.

3) We don't believe we are configured to allow the time to be set by
   remote machines.  The server only 'knows' (at TCP/IP level) about two
   other machines anyway, both of which have the right time and are under our
   control.  (Might we be missing something here?)

4) Our crontabs look good to us.

Paul Smee, Computing Service, University of Bristol, Bristol BS8 1UD, UK
 P.Smee at bristol.ac.uk - ..!uunet!ukc!bsmail!p.smee - Tel +44 272 303132