On 2017-07-31, at 09:50, Robin Vowels wrote: > From: "Charles Mills" <[email protected]> > Sent: Monday, July 31, 2017 2:57 PM > > >> Nay. Many, many instructions are not atomic. On a single CPU, yes. For >> multiple CPUs, not atomic. Until the z13 (?), for example, NI, OI and XI >> were interruptible within a reference to a single byte. NI is actually >> fetch, AND, store. It could be interrupted between the fetch and the store. > > What about the decimal instructions? such as AP, SP, MP, DP, > and others such as NC, OC .... ? > Check the PoOps for "block-concurrent". Little need to repeat the (model-dependendent) list here.
>> So two processors doing NI or OI on the same byte could get "logically >> impossible" results. -- gil
