Date: Sat, 12 Dec 2009 21:41:12 -0500 From: Michael Powell <nightrecon@hotmail.com> To: freebsd-questions@freebsd.org Subject: Re: disk with high frequency noise only on FreeBSD Message-ID: <hg1k8o$okl$1@ger.gmane.org> References: <20091212104900.4587010656B6@hub.freebsd.org> <503306.54962.qm@web65506.mail.ac4.yahoo.com>
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James Phillips wrote: > >> Date: Fri, 11 Dec > 2009 23:52:50 +0200 > From: ly4uk Root <ly41k@ukr.net> >> Subject: disk with high frequency noise only on FreeBSD [snip] > > Now, this post is interesting. I'm sure many people with a software > background may be tempted to write this report off as completely > implausible. The truth is even "non-moving" parts such as inductors > and possibly capacitors can move in response to an applied signal. > For example, my ADSL modem with no moving parts makes an audible > hissing noise louder than the (80mm) fan noise of my BSD server. It is possible for one or more electronic components to emit a noise, even an integrated circuit. This is usually the result of an abnormal operating condition which has established a self sustaining oscillation, which requires some form of feedback loop to operate. The quintessential example is the horizontal output transistor in an analog television or CRT style monitor. These normally operate at about 15KHz but not audibly. When the components around them have altered value enough to change bias voltages they will oscillate and produce a loud high pitched whine. Failure is what eventually occurs in this situation. I had one machine that the memory would "sing" only when a make buildworld was run in FreeBSD. I have an old British Airways movie headphone set from back when their system was acoustic with air tubes. This works really well for examining where a sound is coming from. > I have no idea what would be causing this in 8.0-RC2, but I can > suggest what to look for: anything polling the drive in the audible > frequency range (20 to 20 thousand times per second). Another > possiblity is any action the repeats at that rate, but was not > present in ealier versions. The timer interrupt is in that range, but > other systems like GNU/Linux (before the tickless kernel) and Windows > use a similar timer. There are now 3 timers to choose from, and I think the default changed to the acpi fast timer. Interesting analysis, but very well could be related. > To the original poster: you say this is a laptop. How do you know the > noise is coming from the hard drive and not some other component like > the speakers/Network card/fan? > Regards, > Yes, the noise could be coming from elsewhere. And if it is indeed coming from a VLSI type of chip it does not bode well. This indicates some form of abnormal operation which is most often eventually destructive in nature. There is actually probably very little you can actually do about it, so just live with it and "if it ain't broke don't fix it". When it is broke hit repeatedly with progressively larger hammers until it's in pieces and you now need a new one. -Mike
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