Question on VAX 11/750 clock problem

[wales at ucla-cs.UUCP]

As I assume many readers of this newsgroup are aware, there is (was) a
bug in the VAX 11/750 which frequently causes (caused) the Time-of-Day
Register (TODR) to jump backwards by several minutes after a power off/
on or a push of the RESET button.  The effect of this "jump" is (was) an
incorrect time on the system upon rebooting.

The exact amount by which the clock jumps (jumped) backwards isn't
(wasn't) always the same, and the problem doesn't (didn't) seem to occur
all the time.

Some time ago, Digital came out with a combination hardware/firmware fix
for this bug.  If I remember correctly, the fix involved reading some
patches into the WCS at boot time (in addition to some changed chips on
various boards).

In connection with a paper I am currently writing on time synchroniza-
tion in distributed systems, I would like to find out as much detailed
information as possible about this problem and the way it was fixed.
Specifically:

(1) Exactly what was the problem with the TODR (as specifically and in
    as much detail as possible)?

(2) What factors determined when the problem would occur and how much
    time would be lost from the TODR?

(3) How is it that something in a WCS patch -- read in at boot time --
    could help fix the problem, since the TODR-mangling seemed already
    to have occured on power-up or RESET time (i.e., before a WCS patch
    could be read in)?

Please send any answers to me as mail; I will post a summary to the net.
Thanks in advance for any information.
-- 
Rich Wales // UCLA Computer Science Department // +1 213-825-5683
	3531 Boelter Hall // Los Angeles, California 90024 // USA
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