Path: utzoo!mnetor!uunet!husc6!bu-cs!madd
From: madd@bu-cs.BU.EDU (Jim Frost)
Newsgroups: comp.sys.ibm.pc
Subject: Re: RESET BUTTONS AND HARD DISKS
Message-ID: <19824@bu-cs.BU.EDU>
Date: 11 Feb 88 00:49:20 GMT
References: <3505@batcomputer.tn.cornell.edu> <-497141@cpedev> <662@gethen.UUCP>
Reply-To: madd@bu-it.bu.edu (Jim Frost)
Followup-To: comp.sys.ibm.pc
Organization: Boston University Distributed Systems Group
Lines: 33

In article <662@gethen.UUCP> farren@gethen.UUCP (Michael J. Farren) writes:
>>>I am told that a hardware reset button is a good idea if one has a hard 
>>>disk. Why? 
>
>Because it allows you to do a complete cold boot without powering down
>the disk drive.  If the disk is powered down, and it doesn't have auto-
>parking (as most smaller disks do not), then the heads land wherever
>they happen to be.  This will most likely not be a problem, but it could
>be - you could lose data.  The reset button will allow the heads to keep
>flying, thus never touching the surface, thus preventing this type of
>data lossage.

This isn't necessarily true.  In all but the cheapest (and the very
very expensive) drives, the heads will not touch the surface of the
disk unless the disk is moves (relatively) violently.  This is why you
usually need to park the heads only when you move the drive.  Think of
it this way: drives take several seconds to spin down.  If the heads
were only electronically suspended, they would lose suspension far
before the drive stopped spinning.  The heads would scrape across the
surface of the disk, damaging both the heads and the disk, until the
disk came to a full stop.  Trust me, you'd hear it.

I recall a time back in the CP/M days when a drive that just dropped
the heads was turned off before doing a power down sequence.  The
noise that that thing made was enough to make anyone cry.

The best reason for the reset switch is that the drive doesn't
have to be spun up again.  Spin up is the most strenuous time for a
drive and also for the computer's power supply, and it is best to
avoid doing it more than necessary.

jim frost
madd@bu-it.bu.edu