OPRJ38@TREARN.BITNET (OR) (09/06/90)
I DON'T UNDERSTAND SOME FIELDS.
WHAT ARE CVTTZ, CVTPTR, CVT DSECT ..
AS I UNDERSTAND;
THIS TIME IS 51 BIT MICROSECONDS, AND IT IS UPDATES
EVERY 1 MICROSECOND. CORRECT?
-ORHAN-JAF@UNB.CA ("Tony Fitzgerald 453-4573", 506) (09/06/90)
On Thu, 6 Sep 90 06:09:31 EDT OR <@OHSTVMA.IRCC.OHIO-STATE. EDU:OPRJ38@TREARN.BITNET> writes: > I DON'T UNDERSTAND SOME FIELDS. > WHAT ARE CVTTZ, CVTPTR, CVT DSECT .. These are MVS fields. CVTPTR is at location X'10' decimal 16 in the PSA (Prefix Storage Area) or the first 1K of real and virtual storage in MVS. The CVTPTR is a single word containing the address of the Communications Vector Table, at one time perhaps the single common anchor point for most other OS data areas, still very important in MVS. The CVT dsect is fully described in the MVS/XA Debugging Handbook, LC28-1165, but which may not be available at your site unless you have MVS licensed. It was given in the example, only as one thing that might have to be done to the TOD clock before using it. The field CVTTZ contains an adjustment that must be added to the high order word of the TOD clock in an MVS environment to convert the TOD clock from GMT (Coordinated Universal Time) to Local time. In other systems, other adjustments probably must be made. Thus the argument, use the standard services (the TIME macro in MVS) rather than the TOD clock if you want to calculate dates or times. > AS I UNDERSTAND; > THIS TIME IS 51 BIT MICROSECONDS, AND IT IS UPDATES > EVERY 1 MICROSECOND. CORRECT? Partly, it depends on the speed of the CPU. A fast CPU may update a bit to the right of bit 51, a slow CPU to the left. In any case, whatever bit actually does the counting, it will be as though it were bit 51 every micro second. Note, however, that even the clocks of multi-million dollar IBM CPUs are not 100% accurate and some drift may be expected over time. > > -ORHAN- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- - J. Anthony Fitzgerald Phone: (506) 453-4573 Computing Services NetNorth: JAF@UNB.ca The University of New Brunswick or JAF@UNB PO Box 4400 Fredericton, N.B. Canada E3B 5A3