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Newsgroups: comp.unix.bsd Path: sserve!manuel!munnari.oz.au!uunet!usc!sdd.hp.com!elroy.jpl.nasa.gov!ames!sgi!rigden.wpd.sgi.com!rpw3 From: rpw3@rigden.wpd.sgi.com (Rob Warnock) Subject: Re: Lots of Q's about 386bsd 0.1 Message-ID: <oa5onn0@sgi.sgi.com> Sender: rpw3@rigden.wpd.sgi.com Organization: Silicon Graphics, Inc. Mountain View, CA Date: Sat, 8 Aug 1992 06:20:30 GMT Lines: 28 colin@marsh.cs.curtin.edu.au (Colin Manning) writes: +--------------- | 10) My hard disks are both Maxtor 7040 AT's. Do they really only only have | 5 heads as reported by CMOS, or am I not using a side of a platter?? +--------------- I don't know those particular drives, but a lot of the earlier or smaller drives use the whole bottom surface as a "servo" surface, that is, magic prerecorded data that the drive uses to find and lock onto the tracks (instead of the mechanical detents of *really* old winchesters). So for an "N"-platter disk, one gets "(2*N)-1" usable data surfaces, and hence, heads. [Your disks probably have 3 platters.] Drives with a larger number of platters or tracks have difficulty keeping alignment between the servo surface and the surface being read/written across temperature and position changes, so they use "embedded servo", where the signal from the surface being seek'd on is used to position the heads. "Embedded servo" drives can use both surfaces of each platter for data. -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com Silicon Graphics, Inc. (415)390-1673 2011 N. Shoreline Blvd. Mountain View, CA 94043