From Figure 7-1, page 7-21 of SA23-7832-13, z/Architecture Principles
of Operations, May, 2022:
STORE CLOCK STCK S C ⁸ ⁹ A
STORE CLOCK EXTENDED STCKE S C ⁸ ⁹ A
Lack of a "P" in the " ⁸ ⁹ A" column of the table indicates
instructions are not "privileged". The "⁸ ⁹" notes indicate usage may
be restricted during short periods when in Transactional eXecution mode,
but that does not preclude their use in non-privileged mode in other
contexts.
Back in S/370 days, texts on Assembly Programming might give passing
mention to the existence of STCK and STCKE, but no guidance on usage,
and in my experience they were not considered relevant topics for a
semester programming course. With the proliferation of machine
instructions since those days just to handle the many new data formats
and relative addressing, I would expect the mention of STCK/STCKE in
current instructional texts for Assembler Programming to be even less
likely.
Joel C Ewing
On 3/25/23 12:29, Paul Gilmartin wrote:
On Fri, 24 Mar 2023 23:35:56 -0500, Joel C. Ewing wrote:
... The STCK and STCKE instructions only provide
read-only access to the TOD clock and are not privileged or restricted
by hardware, but they are not taught in programming texts either.
Citation needed.
--
Joel C. Ewing
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