Configuration-z/Architecture-Architecture-Mode and ESA/390-Compatibility-Mode Facilities

[s390guy]

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Note: this issue is closely related to issue #78: "z14 z/Architecture-only mode (CZAM)".

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At one level this is really an ASMA question. But ASMA should do what Hercules does. So, here goes...

At one level it is simply about implementing a new PSW format. But it also puts a stake in the ground relative to ESA/390 support. The PoO suggests these two facilities might be installed separately. But, my understanding is that in practice they will both be present.

We have as near as I can tell merged ESA/390 and zArch in Hercules. ESA/390 is now on a Z box. There is no ability to actually have an ESA/390 machine not on a z box. Now we will need to separate them going forward. I truly believe the ESA/390 Compatibility Mode is also temporary. Not even sure how you get into that mode on a real machine.

I am trying to catch up with ASMA. I am looking at the 2017 PoO when these two facilities were introduced. That is part of why I am asking.

Has anyone thought about the implications?

Harold Grovesteen

[Fish-Git]

Configuration-z/Architecture-Architecture-Mode

Also known as "CZAM", for which, FYI, a GitHub Issue already exists: "z14 z/Architecture-only mode (CZAM)" #78

ESA/390-Compatibility-Mode Facilities

Which, FYI, is already listed in our existing "MISSING Facilities support" #77 GitHub Issue.

Has anyone thought about the implications?

Not really, no. Haven't had any time!   :(

We simply have too much on our plate as it is. Deciding which facility should be worked on next (i.e. which facility takes priority over other facilities) is difficult. As for myself, I tend to choose the ones I personally feel might be the quickest and easiest to complete (*), leaving the trickiest most difficult ones for later (i.e. ones that would likely require much discussion among all of us developers).

But the question whether I have spent much thought on how to implement the two specific facilities you mentioned? (CZAM and 390-Compatibility)

Nope. Not really. Sorry.   :(

BUT ... I'd nevertheless be very interested in hearing others thoughts on the subject, should you wish to discuss it! So I guess it's good that you asked the question, Harold! Thank you!   :)

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(*) Such as Facilities 58 and 61 for example (Miscellaneous Instructions Facility 2 and 3), which I've had coded for quite some time now, but which, oddly, causes z/OS (2.4?) to fail to IPL for some as-yet-unknown reason (the cause of which I haven't had any time to look into due to TXF taking priority).

[s390guy]

The file "CZAM_300-CM" has been uploaded to the hercules-390 groups.io file section. This file describes what is involved in each of the facilities.