Friday question: How far back is PLO instruction supported

and the precursor to PLO is compare-and-swap ... done by C.A.S. at the science center

the first thing had to come up with was a mnemonic that were charlie's initials.

charlie had been done a lot of fine-grain multiprocessor locking on cp67 ... when he invented compare-and-swap. initially trying to get it in the 370 architecture ... the pok owners of the 370 architecture redbook ... aka ... drift warning ... a superset of the prinicple of operations ... basically done in cms script with conditionals ... one conditional got you the full redbook ... the other conditional got the subset published as the pinricple of operation ... this redbook is named for the color of the 3ring binder it was distributed in ... different than the common publications known as "redbooks" available to customers ... now returning to regular schedule programming ...

... the pok owners of the 370 architecture redbook .... said that there wasn't any justification for an smp-specific (locking) instruction ... that the POK operating system people were more than happing with the global kernel spinlock using test-and-set. In any case, to get compare-and-swap justified for 370 architecture ... had to come up with a justification of compare-and-swap use that wasn't smp specific; thus was born the descriptions for compare-and-swap in multi-threaded (interruptable) code (whether running on uniprocessor or multiprocessr).

misc. smp, multiprocessor, compare-and-swap, etc postings

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