Date: Sun, 30 Nov 2008 16:24:37 +0100 From: Gary Jennejohn <gary.jennejohn@freenet.de> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-hackers@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: dd if=/dev/mem can hang a machine? Message-ID: <20081130162437.1bae4371@ernst.jennejohn.org> In-Reply-To: <492FF203.5060405@icyb.net.ua> References: <492FF203.5060405@icyb.net.ua>
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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
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