Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!rutgers!att!mcdchg!ddsw1!ddsw1!karl
From: karl@ddsw1.MCS.COM (Karl Denninger)
Newsgroups: comp.sys.ibm.pc
Subject: A question about hard disk
Message-ID: <2595b4e1:7673.1comp.ibmpc;1@ddsw1.MCS.COM>
Date: 25 Dec 89 06:00:13 GMT
References: <7799@portia.Stanford.EDU>
Lines: 28

>Item 7673 (0 resps) by meric at portia.Stanford.EDU on Sun 24 Dec 89 18:32
>[meric ozcan]    Subject: A question about hard disk
>(8 lines)
>
>
>I have a 60 Mbytes Seagate hard disk (ST-277R-1, RLL type) with autopark
>feature. When the power is turned off there is some strange sound coming
>from the hard disk and it lasts about 5 seconds. It is not the whining
>sound  from the motor. I have never heard this kind of sound from any
>other hard disk. I will try to describe the sound:
>	After you turn off a fan, while it is spinning if you put a stick
>between the fan blades you would get a similar sound. 
>I am really curious about this. Does anyone have any idea?   Thanks.

Yes, it's normal.  It is the heads autoparking.

The drive stores a small amount of power (actually, I believe it is using
regenerative power from the drive motor!) and uses that to park the heads. 
It does this by continually stepping the heads towards the park position. 
Since the platters are spinning when you powerdown, the motor beocmes a
generator.... and provides the power for this.

You may have noticed that the sound slows down and becomes softer as the
motor stops spinning.... because the generator is running out of steam! :-)

--
Karl Denninger (karl@ddsw1.MCS.COM, <well-connected>!ddsw1!karl)
Public Access Data Line: [+1 708 566-8911], Voice: [+1 708 566-8910]
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