On 2019-03-12 12:32, Charles Mills wrote:
Yes, STCK guarantees a unique value. If the clock has not ticked since the last STCK, the CPU has no choice
but to spin until it does. STCKE has smaller "ticks" and so has less of (or no) need for a spin.
STCKF is just like STCK except that it does not guarantee a unique value, and so there is never a need to
spin, and so it is a "fast" instruction. If all you need is "the time" and not a unique
timestamp, always use STCKF. It is a one-character change to your program and may speed it up considerably.
Charles
Going back in time a bit, we were advised by IBM that the performance of
the STCKF instruction is sufficiently better than that of the STCK
instruction that it is worthwhile to write dual-pathed code that uses
STCKF instead of STCK if the machine supports the use of STCKF.
--
Regards, Gord Tomlin
Action Software International
(a division of Mazda Computer Corporation)
Tel: (905) 470-7113, Fax: (905) 470-6507
Support: https://actionsoftware.com/support/
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