7 Mar
2018
7 Mar
'18
7:54 p.m.
On 3/6/18, Clem Cole <clemc(a)ccc.com> wrote:
In the end, BSD4.2 ended up with new time
calls because of that community and started doing things in 100th of second
- which again IIRC was the best the Vax could do.
When all else fails, RTFM. :-)
According to the VAX Architecture Reference Manual (1987), the
Interval Clock Register, which is used by OSes to keep track of real
time, is a 32-bit unsigned value incremented at 1-microsecond
(0.000001 second) intervals.
VAX also has a Time-of-Year Clock Register (colloquially called the
TOY clock), a 32-bit unsigned value whose LSB represents a resolution
of 10 milliseconds (0.01 second). All VAX models except the
VAX-11/730 provided battery backup for the TOY clock so that it
continued to operate even when the system was powered off. A VAX can
thus be powered off for about 497 days and still remember the
date/time.
I think Clem was remembering the TOY clock. It would be the Interval
Clock Register that was used by BSD to implement sleep() and other
time-related services.
-Paul W.