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HP e3000 MPE/iX NTP Hints - May 29, 2001

NTP was first ported to MPE several years ago, but those diffs were never
submitted back to the official NTP distribution.  For more information about
that deprecated port, please see

NTP was re-ported to MPE in May 2001.  What follows are hints learned from
working with NTP 4.0.99k23.  For additional information about NTP on MPE,
please see

MPE lacks the clock-related APIs expected by NTP, so adjtime(), gettimeofday(),
and settimeofday() all had to be implemented from scratch by calling
privileged, undocumented internal OS functions.

Unfortunately the implementation of adjtime() has exposed a sub-second accuracy
bug when slewing the system time.  This bug is documented in SR 5003462838, and
exists on all current versions of MPE.  It has not been fixed at the time of
this writing.  The adjtime() code may possibly need to be altered if/when this
bug is fixed.

This bug has a side-effect whereby the ntpd daemon will screw up the hardware
PDC clock time by many minutes if used for continuous clock adjustments or in
the one-time -q mode.  But note that you can safely run ntpd in order to become
a time server if you include "disable ntp" in the ntp.conf configuration file.

The one-time clock adjustment functionality of ntpdate and ntp_timeset is not
affected by this bug side-effect.  You can safely use these commands to alter
your system time with reasonable accuracy.

The only reference clock that has been tested on MPE is the local clock.  So
building NTP with --disable-all-clocks --enable-LOCAL_CLOCK is strongly

NTP makes use of Privileged Mode (PM) capability in order to bind to the NTP
network port (123) and to access the low-level clock functions.

NTP was ported using the gcc compiler.  Attempting to use the HP C/iX compiler
is not recommended and has not been tested.

Please note that NTP is not an HP product and is NOT supported by HP.  The best
place for asking MPE-specific questions about NTP is the HP3000-L mailing list
at or the associated Usenet
newsgroup of comp.sys.hp.mpe.

The original author of this port is:

Mark Bixby
HP CSY MPE Internet & Interoperability Engineer