Tony, two more things came to mind seeing your name as the original poster.
1.) the KM-family of instructions do all have a query function to indicate what they have and what they can (and you know that). 2.) you could go by what version of the op-sys your software requires. VSE 2.7 ALS1 VSE 3.1 ALS2 VSE 4.1 z-processor VSE 5 z9 the ALSes were not really enforced (IBM never verified the existence of the complete feature-list of ALS1 nor ALS2) (*1). z is defined in first version of POP for z I am not 100% sure how they do it with later versions- I know that z/VSE 4 and above does run on machines that are configured without features usually on these machines. Could be that they use STFL(E) to find what is available or use a DIAG (or other not documented instructions (which can be deciphered reading linux source)). (*1) i.e. UNPKA and PKA were part of ALS1, but FLEX supplied them only on the z-enabled vendor versions. Diving into archives would bring up more- but what is the point. -- Martin Pi_cap_CPU - all you ever need around MWLC/SCRT/CMT in z/VSE more at http://www.picapcpu.de