IBM Mainframe Assembler List <[email protected]> wrote on 11/23/2011 09:36:50 AM:
> > > >Trigraphs are the wrong answer to a question that should never have been asked. > > > >> I feel the same way about the ESEA instruction. > > > > I don't know of any conditions under which you should be > > contemplating using the ESEA instruction. ESEA is intended > > for use by the operating system. > > > Suppose the operating system is open source and the writer is > a developer. > > The lines blur. I interpreted the Original Poster's comment as "The ESEA instruction is the wrong answer to a question that should never have been asked." In ESA architecture, the intended way manipulate the EAX was PC/PR. In z/OS for z/Architecture, we had a specific need to manipulate the EAX while in supervisor state in order to use a special purpose private access list entry which we include on every PASN Access List. We needed to avoid the inconvenience and performance cost of encapsulating all of the code which uses that access list entry into PC routines. For that reason, the ESEA instruction was created. If another operating system is open source, and the writer is a developer, he is free to use ESEA to meet his needs. ESEA is fully documented in Principles of Operation. Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY
