Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!adm!rbj@icst-cmr.arpa From: rbj@icst-cmr.arpa (Root Boy Jim) Newsgroups: comp.unix.wizards Subject: pdp-11/55 Message-ID: <9853@brl-adm.ARPA> Date: Mon, 19-Oct-87 12:38:28 EDT Article-I.D.: brl-adm.9853 Posted: Mon Oct 19 12:38:28 1987 Date-Received: Tue, 20-Oct-87 05:53:47 EDT Sender: news@brl-adm.ARPA Lines: 32 Well, as of 1982 or thereabouts you could build a split I&D kernel and I believe that you could specify it when you linked (TKB'd) a program. Ah, nostalgia... Specifically, RSX-11M Plus. And yes, Ron, the machine had a MARK instruction. I have always thought that the its presence was the main reason DEC avoided using the split I/D space (note for the uninitiated: the MARK instruction executed off the top of the stack, in DATA space), along with the fact that not all models had it. By the time RSX-11M Plus came out, the VAX had already appeared (and as Henry mentioned, so did UNIX, so who cared about RSX anymore). I believe the major use for split I/D space was building shared librarys using supervisor mode I space. Perhaps users were also allowed to specify split I/D space in their TKB as well. As for this discussion being germane to unix-wizards and/or minix, it seems that quite a few of us old-timers used pdp's before UNIX. The release notes for BSD 2.10 mention the possibility of putting some code (was it network?) in supervisor space, and it is not impossible for minix to evolve that way as well if it grows sufficiently. -- David L. Smith {sdcsvax!amos,ihnp4!jack!man, hp-sdd!crash, pyramid}!sdeggo!dave sdeggo!dave@amos.ucsd.edu "How can you tell when our network president is lying? His lips move." (Root Boy) Jim Cottrell National Bureau of Standards Flamer's Hotline: (301) 975-5688 SHHHH!! I hear SIX TATTOOED TRUCK-DRIVERS tossing ENGINE BLOCKS into empty OIL DRUMS..