freebsd-questions Digest, Vol 33, Issue 6

J. Seth Henry jshamlet at
Wed Nov 5 08:22:39 PST 2003

Actually, I have noted this same issue, and both points are correct.

I have a Compaq IA-1 internet terminal which I converted into an X terminal. 
The hardware (was) unmodified, and ran WinCE with no active cooling at all. 
The little machine was perfectly stable, and in fact was designed to never 
completely power down - but instead enter a sleep state when the power button 
was pressed.

I then ran Midori Linux on the system (my first attempt at an X terminal), but 
the X server and mouse driver had some serious issues. Nevertheless, the 
hardware didn't lock up or crash.

I then loaded FreeBSD 4.8-REL on the box, and it started locking up right and 
left. Eventually, I added a cooling fan/ heatsink to the AMD K6-2 CPU, and 
the lockups were greatly reduced. (they still occur, but only under duress). 
Keep in mind, all I changed was the OS - the bus clock and multiplier didn't 
change. Eventually, I installed a K6-III+ mobile processor, and now I very 
rarely get lockups - but it does run noticeably warmer.

This isn't just on AMD hardware, either. I have a dual PIII server that 
suffers the same problem. It runs at least 4-5 degC cooler under RedHat Linux 
(doing the same chores) than it does under 4.8-REL. However, it is a much 
better built system than the IA-1, and doesn't crash, although the cooling is 
so loud that I've been tempted to put Linux back on it just to get rid of 
some of the fans.

The fact is, FreeBSD, for some reason, causes hardware to run hotter. Perhaps 
it is a difference in the idle routine, perhaps it is more "active" about 
checking hardware - I'm no kernel expert. However, this *IS* an issue. For 
those who don't believe the OS can drive the power requirements of a system, 
think again. I installed a SmartUPS on my network, and monitored the load on 
the power supply. Yep - it increased running FreeBSD versus Windows2k.

However, I feel that FreeBSD is, overall, a superior operating system. There 
is no way I would go back to the hell that is linux - much less Win2k. As 
such, I just do a little more homework when buying hardware.

Seth Henry

On Tuesday 04 November 2003 13:42, freebsd-questions-request at 
> Date: Tue, 4 Nov 2003 09:45:51 -0500
> From: Paul Mather <paul at>
> Subject: Re: Overheating attributed to Freebsd --sysctl variables
>         notavailable--
> To: freebsd-questions at
> Message-ID: <20031104144551.GA55894 at>
> Content-Type: text/plain; charset=iso-8859-1
> On Mon, 3 Nov 2003 21:07:45 -0700 (MST), Technical Director
> <trodat at> wrote:
> => Forgive me for saying:
> =>
> => If this system is borked with FreeBSD due to the cpu's not cycling
> => 'down', then use a different operating system. FreeBSD is not
> responsible => for your trouble if you can solve the problem by moving on.
> Doing so and => solving the problem is more important than holding the OS
> and the => contributors to it accountable to something so seemingly far
> fetched. =>
> => One way to test overall integrity of your hardware is to boot to bios
> and => leave it. Does it bake out on you? Then there is definitely
> something => wrong with your hardware, perhaps a fan is spinning less rpms
> than when => new.
> =>
> => In my humble opinion this is probably not associated with the OS, but,
> => that doesn't solve 'your' problem. So besides seeing it for myself I
> can't => see an absolute need to use FreeBSD, in your words the problem,
> and not => use some other [$]NIX.
> =>
> => One last thing, if your CPU's are baking out and crashing, are you not
> => nervous that under load this will happen no matter what the OS? Tweaking
> => system variables will not help you if your server is working ultra-hard,
> => at some point you will reach a mark that your system should still be
> able => to do which currently it can't.
> =>
> => I doubt hardware manufactuers put out equipment that can't run at 100%
> at => least.
> FWIW, I doubt the accuracy of that last paragraph, and don't think
> this is "so seemingly far fetched" at all. :-)
> I have a related problem.  In my case, it's a borrowed laptop on which
> I installed FreeBSD 5.1-CURRENT (quite a while ago, but last
> {build,install}{kernel,world} was circa July 2003).  Also installed on
> the system is Windows 2000 Professional.  The related problem I have
> is that I can fairly easily get the laptop to power off due to
> thermally-initiated shutdown using FreeBSD (complete with "current
> temperature has exceeded system limits" type messages on the console
> beforehand), but can't seem to do so via Win2K. :-(
> Now I know that in a sense this is apples and oranges, because I don't
> do precisely the same things under both operating systems.  But, it
> seems that high-CPU/system activity under FreeBSD will ultimately lead
> to a thermal shutdown, but not on Win2K (no so far as I've been able
> to manage, anyway).  This is inconvenient, to say the least.  For
> example, a FreeBSD buildworld or buildkernel will not complete; it'll
> get part way through before the machine becomes too hot and shuts
> itself down.  Similarly, building "big" ports like Mozilla won't
> complete, which makes portupgrade a bit of fun.  Needless to say, this
> system doesn't get updated much. :-)
> Now I'm not saying the machine doesn't become physically hot when
> running Win2K, too.  It does (e.g., when playing CPU-intensive games,
> etc.).  But somehow, Win2K is able to manage things so that the system
> does not become so hot that the shutdown kicks in.
> So, I'm wondering if there's some sysctl or other knob that can be set
> in FreeBSD that will ameliorate this problem.  (I thought
> laptop/mobile CPUs generally were able to step down to lower clock
> speeds to conserve power/run cooler, for example.)  If I could do
> system rebuilds and port builds without having to restart that'd be a
> big improvement! :-)
> Unlike the original poster, this is an Intel-based system, not Athlon.
> It's a Gateway Solo 450 laptop.  If I didn't know better, I'd think
> that Gateway "engineered" (pah!) this system so it would run Windows
> "okay" and that's it as far as they're concerned. >;-)  FWIW, attached
> at the end of this message is a copy of /var/run/dmesg.boot in case
> anyone can suggest something to help.
> Cheers,
> Paul.
> PS: I'm glad I'm only borrowing this laptop and didn't buy it!!  The
> owner of the laptop only uses Windows, so this is only a problem for
> me running FreeBSD.

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