HP OpenVMS Systems

High-precision time values? (take II)

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The Question is:

 
Have there been any studies of the Repeatablility and Reliability of the
System Clock facilities for Alpha using VMS? If so, can we get Web access to
the study and its results?
 
 

The Answer is :

 
  The OpenVMS Alpha software and Alpha hardware "system clock facility"
  is intended to meet or to (potentially) exceed the system time and date
  accuracy requirements set forth by the Alpha Architecture specifications.
 
  The OpenVMS Alpha software and Alpha hardware "system clock facility" is
  certainly neither intended nor designed to duplicate the functions of a
  time-keeping device such as a cesium clock, for instance.
 
  The OpenVMS Alpha software and Alpha hardware "system clock facility"
  also entirely lacks the crystal temperature stabilization available to
  devices such as the common (metal-backed) wristwatch.
 
  Under both OpenVMS Alpha and OpenVMS VAX, it is quite possible for
  excessive high-IPL system activity (eg: device driver interrupt routines)
  to effectively cause the "loss" of system time by blocking the timely
  processing of the hardware clock interrupts.
 
  Potential approaches could involve the use of NTP or DTSS, of installing
  and using time-keeping hardware, using the Alpha process or system cycle
  counters (rpcc and rscc; topics 2734, 3265, 3375), or other approaches.
 
  Please contact the Compaq Customer Support Center for assistance on
  (potentially) obtaining a more specific answer to this question, to
  discuss the specific details of your particular environment(s) and your
  specific time-keeping requirement(s), and (if necessary) with configuring
  optional or custom or third-party devices (such as a cesium clock) to
  meet your requirements.
 

  

     

     
answer written or last revised on ( 13-DEC-1999 )
     
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