Date: Thu, 02 Dec 2010 13:30:13 -0700 From: Peter Grehan <grehan@freebsd.org> To: freebsd-ppc@freebsd.org Subject: Re: New powerpc64 snapshot Message-ID: <4CF801D5.6090007@freebsd.org> In-Reply-To: <15A958D9-5CBE-4830-B72C-CC4DF2192BC0@gromit.dlib.vt.edu> References: <5A677521-DE86-4BA9-BA85-8003957551B5@freebsd.org> <C31BDA76-ECE9-4012-86C4-24B30ECC8162@gromit.dlib.vt.edu> <4CEBDB9D.2010309@freebsd.org> <15A958D9-5CBE-4830-B72C-CC4DF2192BC0@gromit.dlib.vt.edu>
next in thread | previous in thread | raw e-mail | index | archive | help
> The really bizarre thing, though, is that when the fans begin racing > and the noise is loud, simply executing "sysctl dev.fcu.0.fans" is > enough to calm them down to a more manageable 5600--6400 RPM! Fan control is handled by a microcontroller. If it doesn't see any communication, it assumes that the main CPU has gone away and winds up the fans to full-bore (you can see this if you sit at the FreeBSD loader prompt for a short time). Reading the fan speed is probably enough to fool the micro into thinking that something might be happening, so it will turn the fan speed back to normal and start it's timeout again. later, Peter.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4CF801D5.6090007>