Path: utzoo!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!USCMVSA.BITNET!LDW From: LDW@USCMVSA.BITNET (Leonard D Woren) Newsgroups: comp.lang.asm370 Subject: Re: New System/3x0 Instruction Message-ID: <9103181105.AA23149@ucbvax.Berkeley.EDU> Date: 18 Mar 91 11:04:00 GMT Sender: usenet@ucbvax.BERKELEY.EDU Reply-To: IBM 370 Assembly Programming Discussion List Distribution: inet Organization: The Internet Lines: 32 > Leonard, I think you are splitting hairs here, that kind of assist > "instruction" is really just a subroutine of the operating system that IBM > has decided to make faster by implementing in microcode. They know a lot > about the operating system in question and as you noted, they can modify > control blocks of that operating system. However, to call them "instructions" > seems to be going a bit far. Ok, now that we have nitpicked the terminology to death, let's think about what started this -- a request for a new instruction which would switch two pages in the page tables. Since this can clearly be done as an MVS service via an SVC, it can also be done as an assist instruction. One big problem that I have with exotic instructions is that they aren't on all 370s/390s/whatever. I have yet to find a machine that has MVCIN. Has anybody worked on a machine that had the math assists (SQRT and trig functions)? I'm still reluctant to write code using BAS and BASR, since they don't exist on non-XA machines. Suppose I use an MVCIN instruction? Either: (1) You can only run it on a machine that has MVCIN, if you can find one, or (2) I have to write dual path code so that it works on a machine without MVCIN. At which point I won't bother to write the code in the first place which uses MVCIN. Be careful what you ask for. You may get it. (However, asking for an instruction to be added to the standard instruction set and therefore always installed on all models is not likely to happen.) /Leonard