On Mon, 26 Feb 2018 17:07:50 +0000, Seymour J Metz wrote:
>Timer units are the same for the S/360 and the S/370. From GA22-7000-4 :
>"In each case, the frequency is adjusted to give counting at 300 cycles per
>second
>in bit position 23. The cycle of the timer is approximately 15.5 hours. "
>
With some aritmetic:
503 $ rexx
say 2**23 / 300 /60 / 60
7.76722963
So, this gives counting at one cycle per 7.77 hours in bit position 0.
What does "counting at [n] cycles per [unit]" mean?
How can this agree with the description of the TIMER macro? :
For TUINTVL, the address is a fullword containing the time interval.
The time interval is presented as an unsigned 32-bit binary number;
the low-order bit has a value of one timer unit (approximately
26.04166 microseconds).
Again, some arithmetic:
506 $ rexx
say 1000000 / 300 / 2**( 31 - 23 )
13.0208333
13.020833 µsec, not 26.04166.
-- gil
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