Jumping R/T clock

[P E Smee]

In article <8245 at brazos.Rice.edu> P.E.Smee at gdr.bath.ac.uk writes:
>X-Sun-Spots-Digest: Volume 9, Issue 188, message 3
>
>We're having problems with the real-time clock on a SPARCserver 330 (SunOS
>4).

Had several responses to my plea.  I've tried to respond to them all, but
a couple of them bounced.  Many were 'if you find out, tell me'.  There
were enough of those that I suspect there are even more I haven't heard
from, so would like to also post my synopsis in the news.

Scott Leadley (cc.rochester.edu) offers:

> This is a known problem with SunOS 4.0.n on the Sun 4/330.  Sun may
> have have a bug fix for it, but the workaround that they gave us (a
> couple of months ago) is to put:
> 
> 	0 21 * * * /bin/date -a 1 1> /tmp/datelog 2>&1
> 
> in the root crontab.

His surmise is that the hardware TOD clock remains correct (because his
system seems to come up with the right time if you reboot), and that it is
the software 'kernel clock' which slips.  And that date -a might force the
kernel to resync with the hardware.  From Sun's response (below) this
sounds likely.  Though I would expect that it wouldn't STOP the jumps, but
simply force you back into sync now and again so you didn't get too far
out.  (On the other hand ours only jumps once or twice a week, so maybe a
daily resync would do it.)

Ralph Finch (California Dept of Water Resources) mentioned that there were
patches for this.  Actually, he even offered to send them.  I passed on
this.  Our root is paranoid and won't allow anything on the system unless
he personally knows the originator (or at least who he can sue :-), or can
check it myself.  And I can't expect the other staff people to obey my
rules unless I do.

However, this was still very useful, as it meant that it wasn't us doing
something stupid.  It's a new machine type for us.  We couldn't believe
that a 30000 pound (sterling, more or less -- not sure what we actually
spent) machine couldn't keep time as well as my 30 pound wristwatch, so
were convinced it was us.  Armed with this, we went after Sun technical
support hotline.  They provided us with a one location patch -- in fact, a
1-bit patch -- to apply in 3 places.  (Object patch; we didn't get a
source license.)

I don't expect you to trust me any more than I trust strangers, so I'm not
gonna tell you what it is.  Besides, I don't know what, if any, mods
you've made to things, or if UK SunOS is identical to US SunOS.  Ring your
Sun support center.  The official Sun description is:

| There is a bug in SunOS 4.0.3 which causes the Sun 4300 processor board to
| be unable to synchronize the kernel's notion of the time of day with the
| TOD chip.
|
| This applies ONLY to SunOS 4.0.3 for the Sun 4 ...

Tell them you know about their guilty secret, and you want the answer.

Thanks everyone.  Cheers...

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