Does OS "tick" clock sync with CMOS clock periodically?

[Greg Lindauer]

My company is sending a group of four Windows 2000
Professional machines, SP2, set up in a workgroup without
the w32time service running. We noticed that one of the
machines has a clock that drifts wildly, but then "resets"
at the top of some hours. The result is that, over time,
the clock (date/time under control panel) has a slight
drift with respect to the other machines, but in the short
term you can often see it off by between 10 seconds to a
minute before it seems to automatically reset.

We don't have any time service running, so we are wondering
if this can be explained by something happening in Windows
2000. While it is running (between restarts), does Windows
2000 periodically synchronize its clock (which presumably
is updated from a tick counter from an interrupt on some
timer device) with the CMOS realtime clock on the Motherboard?

 

[Greg Lindauer]

An update: It appears that a Windows 2000 machine not
connected to a server (not using w32time) does in fact
update its own clock once it determines its clock has
drifted more than a minute from the CMOS real-time clock.
We've tested this pretty extensively.