John, give a lowly creature (like an HLASM-programmer on VSE) a chance to say something....
What does MODE=NONXM imply versus MODE=FULLXM? I do have ideas about the reason. Is NONXM the old original method?...is FULLXM the method for passing values in AR-mode? could it be that they need a register that is backed by an AR for passing something - and 0 is the only one with no backing (good enough for addresses of code anyway) -- Martin Pi_cap_CPU - all you ever need around MWLC/SCRT/CMT in z/VSE more at http://www.picapcpu.de
