That condition would eliminate the SLR that I suggested in an earlier post, as well as LA, but I don't know if that condition existed. I do know that the module was supposed to return zero in R15 for proper processing by the Initiator/Terminator.
Bill Fairchild Rocket Software -----Original Message----- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Chase, John Sent: Monday, November 29, 2010 10:51 AM To: IBM-MAIN@bama.ua.edu Subject: Re: IEFBR14 Wasn't there also a requirement that whatever means was chosen to zero Reg15 also set the condition code to zero? > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of J R > Sent: Monday, November 29, 2010 10:44 AM > To: IBM-MAIN@bama.ua.edu > Subject: Re: IEFBR14 > > He also omitted Exclusive Or (XR 15,15), unless that's what he meant by "Clear Register". > > > > Date: Mon, 29 Nov 2010 16:08:33 +0000 > > From: bi...@mainstar.com > > Subject: Re: IEFBR14 > > To: IBM-MAIN@bama.ua.edu > > > > He meant three possible instructions that only occupied two bytes of storage, I believe ("All three > required the same memory and processing cycles. They were equal and interchangeable."). LA is a 4-byte > instruction. A number of 4-byte instructions that were available way back when comes to mind: e.g., L > R15,=F'0'; LM R15,R15,=F'0'. > > > > Each byte of "core" storage in the 1960s was extremely scarce. He also omitted Subtract Logical > Register 15,15, which is a 2-byte instruction and which executed slightly faster on a S/360 model 30 > than Subtract Register. > > > > But you are right; there is no Clear Register instruction. > > > > Bill Fairchild > > Rocket Software > > > > -----Original Message----- > > From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Shmuel Metz (Seymour > J.) > > Sent: Monday, November 29, 2010 7:25 AM > > To: IBM-MAIN@bama.ua.edu > > Subject: Re: IEFBR14 > > > > In <listserv%201011282257541113.0...@bama.ua.edu>, on 11/28/2010 > > at 10:57 PM, Avram Friedman <ibmsysp...@geek-sites.com> said: > > > > >http://www.miketaylor.org.uk/tech/oreilly/more-iefbr14.html >From one > > >of the two IBM co-authors > > >Note not part of the original OS spec added as an after thought > > > > Given the following quote, his memory is not reliable: > > > > There were three possible instructions that could be used to > > zero R15: ``Clear Register R15'', ``Subtract Register R15,R15'', > > and ``Exclusive Or Register R15,R15''. > > > > There is, of course, no "Clear Register" instruction. The third > > obvious instruction is LA. > > > > -- > > Shmuel (Seymour J.) Metz, SysProg and JOAT > > ISO position; see <http://patriot.net/~shmuel/resume/brief.html> > > We don't care. We don't have to care, we're Congress. > > (S877: The Shut up and Eat Your spam act of 2003) > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, > > send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO > > Search the archives at http://bama.ua.edu/archives/ibm-main.html > > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, > > send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO > > Search the archives at http://bama.ua.edu/archives/ibm-main.html > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO > Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
