Date: Mon, 8 Sep 1997 02:43:25 -0400 From: Lee Cremeans <lee@wakky.dyn.ml.org> To: Mike Smith <mike@smith.net.au> Cc: chat@freebsd.org Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI) Message-ID: <19970908024325.42427@wakky.dyn.ml.org> In-Reply-To: <199709080546.PAA01604@word.smith.net.au>; from Mike Smith on Mon, Sep 08, 1997 at 03:46:35PM %2B1000 References: <19970908013227.32344@wakky.dyn.ml.org> <199709080546.PAA01604@word.smith.net.au>
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On Mon, Sep 08, 1997 at 03:46:35PM +1000, Mike Smith wrote: > > > > PS: When did the first voice-coil-seek hard drives come out? This is a > > question that's been bugging me for some time now... > > Linear or rotary actuator? The linear VC actuator probably predates > the use of stepper motors; certainly some of the more impressive > magnets in my collection started their lives in disk units. Makes sense...I had an old (1985) Seagate ST-4026 that used linear seek, and the magnets in it were HUGE. There's also a Hitachi DK511-8 here, of about the same vintage, that uses rotary voice-coil. > High-precision stepper motor controls are more complex than the linear > displacement sensor approach that you use with a linear VC actuator too; > it's the mechanicals and the space that made steppers cheaper, AFAIK. Yep...most stepper-motor drives I've seen used rack-and-pinion and sector-and-pinion linkages, joined together with bands or gears--about the same as a floppy drive. How they got those things to track accurately is beyond me, though. Also, you should see the hoops Seagate jumped through to make the ST-251 do 820 cylinders AND auto-park...thing actually used a 5-phase stepper! It also had a dedicated sequencer chip to run the stepper off the spindle's back-EMF to park the heads. There's even weirder auto-park systems around; I've seen one that actually pulled the heads away from the disks. But I digress... :) -- Lee C. -- Manassas, VA, USA (WakkyMouse on DALnet #watertower) A! JW223 YWD++^i WK+++r P&B++ SL++^i GDF B&M KK--i MD+++i P++ I++++ Did $++ E5/10/70/3c/73ac Ee34/1/36 H2 PonPippi Ay77 M | hcremean (at) vt.edu FreeBSD/Linux/Unix hacker...Win95 and M$ evil! (go see www.freebsd.org) My home page: http://wakky.dyn.ml.org/~lee | finger me for geek code
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