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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 http://www.bixby.org/mark/xntpix.html.
+
+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 http://jazz.external.hp.com/src/hp_freeware/ntp/.
+
+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
+recommended.
+
+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 http://raven.utc.edu/Archives/hp3000-l.html 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
+mark_bixby@hp.com