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From: Luigi Rizzo <luigi@labinfo.iet.unipi.it>
Message-Id: <199601221524.QAA05424@labinfo.iet.unipi.it>
Subject: Re: dd /dev/mem ...
To: mpp@mpp.minn.net (Mike Pritchard)
Date: Mon, 22 Jan 1996 16:24:34 +0100 (MET)
Cc: bugs@FreeBSD.org
In-Reply-To: <199601221436.IAA00318@mpp.minn.net> from "Mike Pritchard" at Jan 22, 96 08:35:41 am
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> Luigi Rizzo wrote:
> > 
> > Running 2.1R, I tried the following running as root:
> > 
> >     dd if=/dev/mem bs=32k skip=512 count=1 | dd bs=32 count=1 | hexdump
> > 
> > and my P100 w/ 16MB was frozen: no keyboard, no mouse, everything
> > still on the X screen.
> 
> Funny you should mention this -- I just crashed my machine trying
> the same thing trying to verify PR# 383.  As near as I can tell, it
> only locks up the machine when you run it from X *and* the current
> vty is the X window.  If you do something like:
> 	sleep 30; dd if=/dev/mem ...
> and then switch to vty0, the machine won't lock up.  Running from
> an ordinary syscons vty doesn't seem to be a problem.

Right, I think it worked yesterday from a syscons vty.

and I believe I have read from /dev/mem with a C program from an
xterm with no problems either.

	Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================