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Date: Sun, 30 Nov 2008 16:24:37 +0100
From: Gary Jennejohn <gary.jennejohn@freenet.de>
To: Andriy Gapon <avg@icyb.net.ua>
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Cc: freebsd-hackers@freebsd.org, freebsd-hardware@freebsd.org
Subject: Re: dd if=/dev/mem can hang a machine?
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On Fri, 28 Nov 2008 15:28:35 +0200
Andriy Gapon <avg@icyb.net.ua> wrote:

> 
> I have a new machine with DG33TL mainboard (ICH9/G33).
> In a course of some hacking I ran dd if=/dev/mem ... to scan all memory,
> this caused the machine to hang.
> I tried to reproduce and this is 100% reproducible.
> 
> I am not used to such behavior. In older days I could scan all the
> memory without any issues.
> 
> Could this be related to some modern form of memory-mapped IO? Or to
> Intel Management Engine (that seems t bite into DRAM)?
> Or something else?
> 
> Just wondering.
> 

That's what I would assume.  With some hardware just reading a register
can be harmful.

---
Gary Jennejohn