Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!sics.se!uplog.uppsala.telesoft.se!uplog.uppsala.telesoft.se!thomas From: thomas@nexus.se Newsgroups: comp.unix.questions Subject: Re: why different swapping modes on executables? Message-ID: Date: 26 Mar 91 09:54:05 GMT References: <1991Mar12.012401.557@nowhere.uucp> <1991Mar12.104352.23097@kithrup.COM> <573@adpplz.UUCP> Sender: news@uppsala.telesoft.se (news) Followup-To: comp.unix.questions Organization: Communicator Nexus AB Lines: 25 In-Reply-To: martin@adpplz.UUCP's message of 13 Mar 91 20:27:43 GMT In article <573@adpplz.UUCP> martin@adpplz.UUCP (Martin Golding) writes: My impression is that the (original) version of the Magic Number was the actual value to load into the PDP 11 MMU control register, to select one or the other model. Actually the magic numbers for the PDP11 was a branch instruction that made the processor jump past the header. Writeable text (code was trated as data) had 0407 which meant jump 7 words forward and read/execute-only text had 0410 which meant jump 8 words (the magic numbers were in octal) forward. I don't know whether the magic number actually WAS executed, it sure could have been. There was also a 0411 which was separate I and D spaces. Pageable objects have 0413, don't know if this was ever used on a pdp11. Thomas -- Real life: Thomas Tornblom Email: t_tornblom@nexus.se Snail mail: Communicator Nexus Phone: +46 18 171814 Box 857 Fax: +46 18 696516 S - 751 08 Uppsala, Sweden