Submission for mod-computers-68k

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2 total messages Started by bet Wed, 11 Feb 1987 17:05

#132

Author: bet
Date: Wed, 11 Feb 1987 17:05

29 lines
1825 bytes

Path: dukeac!bet
From: bet@dukeac.UUCP (Bennett Todd)
Newsgroups: mod.computers.68k
Subject: Re: Minix/68k
Message-ID: <359@dukeac.UUCP>
Date: 11 Feb 87 17:04:59 GMT
References: <8702081739.AA11278@gorgo.att.com>
Reply-To: bet@dukeac.UUCP (Bennett Todd)
Organization: Duke User Services, Durham, NC
Lines: 18

OS/9's multitasking model won't help either UNIX or Minix run well on a plain
68000 without MMU; someone mentioned earlier that it doesn't relocate a
process after the process has begun executing (I don't know OS/9; if that was
incorrect then discount this whole note). UNIX (and Minix) found their notion
of multitasking on the fork() system call, which makes two (almost) identical
processes out of the one which invokes it. The two then continue executing
independently. This requires, at a minimum, the ability to duplicate memory
allocated to data, and allow two separate images to proceed executing. Unless
tasks are going to swap on every context switch, the data area has to be
relocatable (including pointers to data and subroutine return addresses on the
stack).

-Bennett
-- 
Bennett Todd, Duke User Services, Durham, NC 27706-7756; +1 919 684 3695
UUCP: ...{philabs,akgua,decvax,ihnp4}!mcnc!ecsvax!dukeac!bet
BITNET: DBTODD@TUCC

Re: Submission for mod-computers-68k (really Nuxi fork())

#143

Author: jejones
Date: Fri, 13 Feb 1987 14:04

10 lines
981 bytes

The earlier mention was right; a OS-9 process's data memory does not get
moved.  (Of course, 99.9+% of programs under Unix that use fork() read

	if (fork() == /* whatever says I'm the child */)
		exec[a-z]*("what I really wanted to run", ...);

so I don't think that OS-9's at any great loss for not having Unix's
fork().)

		James Jones

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