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 .... ?
So two processors doing NI or OI on the same byte could get "logically impossible" results.
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