On 2017-07-31, at 18:41, Robin Vowels wrote: > >> I think (TS) Test and Set was/is atomic and AFAIK was the earliest >> implemented >> atomic instruction. > > I think that the entire /360 user instruction set would have been of that > kind. > > AFIK there was no provision to suspend any instrction and to resume it > after an interrupt. > The instruction had to be allowed to complete, and the IAR saved, > so that when control was passed back to the interrupted program, > the next instruction was executed. > Multiprocessors with common memory vitiated that form of atomicity, thereby breaking NI, OI, XI, and many others.
-- gil
