Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ucbcad!pasteur!ucbvax!cbosgd!mandrill!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.amiga
Subject: Re: Power Supplies in Amigas
Message-ID: <953@neoucom.UUCP>
Date: 18 Jan 88 03:59:53 GMT
References: <2299@crash.cts.com> <2055@gryphon.CTS.COM> <1828@rayssdb.RAY.COM>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 38
Summary: Hard disks do not like to shut off frequently


ST-506/412, ESDI, SCSI, etc. 5-1/4 inch hard disks usually have an
integrated drive motor that is part of the spindle assembly.  The
spindle usually employs a sleve bearing and is thus very impervious
to wear  -- it doesn't need ball bearings since there is no
laterally applied load.  I have a hard drive in an AT compatible
that has excessive bearing runout which makes the heads jam when
the drive is powered down -- the heads stop flying as the drive
slows down and actually stick to the platter like gague blocks
stick because the platter and heads are so smooth.  Needless to say
this drive stays on all the time. -- The sticky heads require a
manual flip of the flywheel to get the drive going, as the internal
motor doesn't have enough torque to break free.

Also, nastyness is most likely to occur as the drive spins up or
down because the heads really are not flying.

MTBF ratings for consumer drives range 20K to 30K hours.  I'd say
that with times like that, that you might as well leave the hard
disk on continuously while the computer is on.

Modern hard disks are quite different from the monsters that graced
CP/M computers.  I still have a Persci voice coil 8" floppy drive
somewhere -- boy was I glad to take that abomination out of
service.  Shugart 801s were pretty good 8" drives as long as the
helical stepper motor shaft was kept clean.  Since those drives had
110 volt synchronous motors, they did get kind of warm, so I agree
that powering then down after a few minutes of inactivity was a
good idea -- also minimized wear on the diskette not to have it
turning continuously.  I never had the funds to get a hard disk on
any of the CP/M systems I had.

I also agree that shutting down monitors during inactivity is a
good idea as it minimizes the pickup of dust on the high voltage
wiring and thus reduces the likelyhood of a short on the high
voltage supply.  I make the assumption that software can be
employed to do screen blanking.

--Bill