In <m339gsf99o....@garlic.com>, on 08/23/2011
at 11:16 AM, Anne & Lynn Wheeler <l...@garlic.com> said:
>lower-end 360s would update location 80 appox. every 3mills
No. From S/360 PoOps:
"Timer feature
The timer is provided as an interval timer and may be programmed to
maintain the time of day. The timer consists of a full word in main
storage location 80. The timer word is counted down at a rate of 50
or 60 cycles per second, depending on line frequency. The timer word
is treated as a signed integer following the rules of fixed-point
arithmetic. An external interruption condition is signaled when the
value of the timer word goes from positive to negative. The full cycle
time of the timer is 15.5 hours.
An updated timer value is available at the end of each instruction
execution but is not updated in the stopped state. The timer is
changed by addressing storage location 80. As an interval timer, the
timer is used to measure elapsed time over relatively short intervals.
It can be set to any value at any time."
I recall a frequency of 300 Hz on faster models, but don't recall
whether that came in with the S/370. The high resolution timer was a
special feature and included a cache for locations 80-83.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT
ISO position; see <http://patriot.net/~shmuel/resume/brief.html>
We don't care. We don't have to care, we're Congress.
(S877: The Shut up and Eat Your spam act of 2003)
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