Right.
A near defective fan is detected by loosing RPM. But even with high quality
fans, sometime they slow a little bit. So you must wait one hour before
halting your computer (but dont wait if it stop !). From memory, optimal
speed is 6000 rpm, and I put an alert on a 15% loss.

----- Original Message -----
From: "Ty Sarna" <tsarna@endicor.com>
Newsgroups: netbsd.port.i386
To: <port-i386@NetBSD.ORG>
Sent: Tuesday, December 26, 2000 11:07 PM
Subject: Re: via environmental monitor
>
> Actually, keeping an eye on the fan RPMs seems even more important to
> me, in that if a fan is stating to go (I've heard 10% loss from initial
> revs suggested as a "time to replace fan" metric), you get a chance to
> do something about it before damage happens.  If you're not monitoring
> the fan and it siezes, you by the time the CPU temp monitoring notices,
> you don't have much time to do anything except maybe "halt -p", if
> you're lucky :-)