ActualIy, I am interested, and was since it made its first appearance on S/360, but unless you're writing DAT-OFF code you don't need to deal with it.
-- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> on behalf of Steve Smith <sasd...@gmail.com> Sent: Wednesday, November 6, 2019 1:44 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: Questionable Instructions in Obtaining EAX documentation Prefixing is absolutely* irrelevant to this discussion, and to 99.99% of assembler programmers for their entire lives. It's well-documented if you're interested, but you probably aren't. Any discussion here is very likely to be spurious, specious, and superficial. *I guess it's "really" irrelevant too. :-) sas On Wed, Nov 6, 2019 at 1:30 PM Seymour J Metz <sme...@gmu.edu> wrote: > The contents of R0 is irrelevant to forming the effective address of an RS > or RX instruction. the contents of the prefix register are only relevant > for real addresses. > > Now,, if you're running DAT off and you use an instruction that takes an > address from a register, e.g., MVCL, then it is subject to prefixing. But > even there it's in terms of the storage assigned to the LPAR. >
