[hercules-390] DAT-Enhancement Facility 1/2 versus Enhanced-DAT Facility 1/2

['\'Fish\' (David B. Trout)' [e-mail] [hercules-390]]

Can someone please confirm for me, within a high degree of confidence, that the "DAT-Enhancement Facility 2" does not (and never did!) have any STFL/STFLE facility bit assigned to it?

While reviewing the latest list of facilities documented in the SA22-7832-11 Principles of Operation manual, I noticed that bit 3 is documented as pertaining to whether the DAT-enhancement facility is installed or not (which chapter 1 refers to as "DAT-enhancement facility 1" instead of just "DAT-enhancement facility" (presumably to distinguish it from "DAT-enhancement facility 2"), even though the rest of the manual just uses the term "DAT-enhancement facility" without the "1").

Facility bits 8 and 78 however, are documented as pertaining to whether the Enhanced-DAT facility (1 and 2 respectively) are installed or not.

Without a facility bit assigned to it, how can one know whether "DAT-enhancement facility 2" is installed or not? Does one simply presume that if facility bit 3 ("DAT-enhancement facility") is on/set, that that also means "DAT-enhancement facility 2" is also installed? Does facility bit 3 pertain to BOTH "DAT-enhancement" facilities? (Both 1 and 2?)

I'm more than a little confused by all this.

At least the two "Enhanced-DAT" facilities ("Enhanced-DAT facility 1" and "Enhanced-DAT facility 2") both have separate facility bits assigned to them (bits 8 and 78 respectively), but the same is not true for the two "DAT-enhancement" facilities.

Can someone please confirm for me, within a high degree of confidence, that the "DAT-Enhancement Facility 2" does not (and never did!) have any STFL/STFLE facility bit assigned to it?

Thanks!

['Peter J. Jansen' [e-mail] [hercules-390]]

Fish,

I am not sure whether my opinion in this can be regarded as one with a "high
degree of confidence", but my understanding is that indeed "DAT Enhancement
2" (= D2) does NOT have a STFL/STFLE facility bit assigned. I also assume
that "DAT Enhancement" without either a "2" or a "1" implies "DAT
Enhancement 1" (= DE), and that when DE is present (facility bit 3), only
executing an LPTEA instruction yielding an operation exception (or NOT)
means that D2 is also present (or NOT).

Indeed confusing as the "Enhanced-DAT 1/2" (= EDAT-1 / EDAT-2) each have
their own facility bits (8 / 78).

I think I somewhere read that VM used to not rely on STFL/STFLE facility
bits, and that the current z/VM very often still does not do that. But
whether this is (or was) true I certainly do not know for sure.

Cheers,

Peter J.

['\'Fish\' (David B. Trout)' [e-mail] [hercules-390]]

Peter J. Jansen wrote:

[...]

only executing an LPTEA instruction yielding
an operation exception (or NOT) means that D2
is also present (or NOT).

I've come to the same conclusion. Even though the "Programming Note" on page 4-101 of the SA22-7832-11 Principles of Operation manual discourages doing so, I can see no other choice!

Thanks for the feedback.