My understanding is that IBM uses DIAG as a hypervisor call for the version of CP buried in PR/SM. I don't know how close the interface is to that used by CP in z/VM.
My understanding is that an OS in n LPAR runs in a mode that does not allow any instructions intended for use only by millicode. Even in XA SIE could suppress some facilities. Those instructions are not part of the architcture. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 עַם יִשְׂרָאֵל חַי נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר ________________________________________ From: IBM Mainframe Discussion List <[email protected]> on behalf of Paul Gilmartin <[email protected]> Sent: Wednesday, June 18, 2025 12:22 PM To: [email protected] <[email protected]> Subject: Re: Is there an equivalent of an S-con for a long displacement? External Message: Use Caution On Wed, 18 Jun 2025 11:13:19 -0500, Adam Johanson wrote: >Michael wrote: > >> On z/Architecture, are there instructions that the machine will execute that >> are not following the Principles of Operation documentation? Or would all >> such instructions get a specification exception? > Diagnose? I believe its existence is documented; otherwise, "model dependent". And no mnemonic. >It's my understanding that millicode instructions are "real" instructions with >opcodes and such that are simply not documented. I also heard that they have >their own set of registers to use. > >Could be wrong, though. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
