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From: jab@uokvax.UUCP
Newsgroups: net.unix
Subject: Re: need memory syscall - (nf)
Message-ID: <6100031@uokvax.UUCP>
Date: Sun, 6-May-84 13:41:00 EDT
Article-I.D.: uokvax.6100031
Posted: Sun May  6 13:41:00 1984
Date-Received: Wed, 9-May-84 01:46:25 EDT
References: <29300011@uiucuxc.UUCP>
Lines: 19
Nf-ID: #R:uiucuxc:29300011:uokvax:6100031:000:913
Nf-From: uokvax!jab    May  6 12:41:00 1984

#R:uiucuxc:29300011:uokvax:6100031:000:913
uokvax!jab    May  6 12:41:00 1984

On the v7 systems, there was a "research" system call called "phys()" that
allowed you to poke things into your pdp-11 segmentation registers. You
could, for example, map the I/O page into your address space and output
to the console by polling the DL11/KL11 that talks to the console terminal.
One person I know used it every once in a while as a glorified way to patch
tty structures that were wedged because of some weird dh11 code.

It's not on system {III,V}, and not in anything on a vax, because it's
terribly machine-dependent and unless you have something that looks like
old-fashioned segments, amazing things can happen. I can imagine what happens
if you try to talk to something in a Unibus space on a vax and it's not there...
(It's not polite enough to bomb your process off with a segmentation violation,
like on the 11, but instead will probably croak the kernel itself.)

	Jeff Bowles
	Lisle, IL