Path: utzoo!mnetor!uunet!husc6!mailrus!nrl-cmf!ames!oliveb!sun!pepper!cmcmanis
From: cmcmanis%pepper@Sun.COM (Chuck McManis)
Newsgroups: comp.sys.amiga
Subject: Re: Warm Reboot and Hard Disk Noise
Message-ID: <51959@sun.uucp>
Date: 4 May 88 17:03:08 GMT
References: <8804300422.AA18746@decwrl.dec.com> <12083@tut.cis.ohio-state.edu> <20570@sci.UUCP> <3718@cbmvax.UUCP>
Sender: news@sun.uucp
Reply-To: cmcmanis@sun.UUCP (Chuck McManis)
Organization: Sun Microsystems, Mountain View
Lines: 27

In article <3718@cbmvax.UUCP> hedley@cbmvax.UUCP (Hedley Davis) writes:
->How about this:
->
->	The system boots, and the driver comes up and says 'Is the disk
->at track zero ?'. The disk isn't, nor does the disk even know where it
->s own head is. The veiw of the world here is a single bit which says
->'Is the head over track zero ?'. Now, we could tell the disk to seek
->a few hundred tracks over, but then  if the disk was on track 5 , it
->would come rushing back towards track zero, and WHAM, hit the head stop
->with incredible velocity. This would not be a good thing.

No offense Hedley but that is what you get for programming a hard disk
like a floppy. How about this :

The system boots and the driver comes up and says "I wonder what cylinder
the disk is on?" So it issues a READ-ID command which causes the heads to
read the first sector header they happen to come upon and return the cylinder
number. Remembering this, it tells the drive to seek to the position of the
root block. No noise, no fuss. SCSI drives are even easier because they
have no idea what the heck a cylinder is. You just say "Go to logical block
207" or whatever and they do. Anyway, it could be made to work better.
Your explanation does explain the noise though...


--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.