297 lines
16 KiB
Plaintext
297 lines
16 KiB
Plaintext
Some opinions on leaving your computer on 24 hours a day and mounting
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your machine sideways.
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===============================================================================
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This is the version that was included in the Frequently Asked Questions
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file until May 1990:
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There's a lot of stress placed on the system when it first comes up.
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Generally, you should leave your system running if you plan to return
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within the next few hours or so; if you don't expect to be using it for
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a day or so, whether or not you turn it off is a personal judgement call.
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Monitors aren't the same, though, since images can get "burned into"
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the phosphor. Use a screen blanker, or turn it off if you'll be away
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for more than five or ten minutes.
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As for mounting it sideways: The most common myth about this is that
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it will make the disk drive bearings wear unevenly. If you look at the
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manufacturer's information when you buy a disk drive, you will see
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that it is warrantied in any position *except*upside-down* (with the
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defect label down). However, the disk may hang slightly differently in
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the bearings after being placed on its side, so if you plan on
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mounting your system sideways, you should back up your hard disk while
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it's level, then mount your system sideways and do a low-level
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reformat of your hard disk and restore it from the backup you made. If
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you do this you shouldn't have problems.
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===============================================================================
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From: chuck@eng.umd.edu (Chuck Harris)
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Subject: Computer on 24hrs.day?
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Date: 30 Mar 90
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I can provide some info on the phenomonon. Semiconductors have failure
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curves that look like:
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Failures||
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| \ /...
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| \ /
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|_____\______________ ... ___/__
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0 100 1E6 = ~100 years
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Hours of use
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The failures in the first 100 hours are some times called Infant mortality.
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I'm not sure at all about the 1E6 hours (Lets say it's a lot of hours!)
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The first 100 hours failures are the reason the most reputable manufacturers
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will "Burn-in" new systems. Statistics shows that there is little gain in
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confidence by burn-ins much longer than 100 hours.
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NASA (I think) found that semiconductors that had been left on for a long,
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long time were very likely to fail if their power was cycled off then on again.
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However, statistics showed that the same semiconductor if just left on would
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continue to work almost indefinitly.
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As I recall the failures due to cycling power occured while the power was off.
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it had something to do with the transistor's junctions migrating too close
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together while power was off, then when power was turned on, the transistor
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failed because the junctions were shorted. (power being on continuously
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apparently prevents this) Anyone know more about this?
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These are the tests that everyone alludes to when they tell you to leave
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computers and other electronics on all the time for greater life. They
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only mean something if you have a statistically large number of transistors
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(the transistors need to be from different lots not just a large number on an
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IC) in your system, and you are using the system for a LARGE number of hours.
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Your individual PC does NOT have a statistically large number of semiconductors
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in it. The entire country's PC's do. 100 years is a long time.
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Conclusions that I think you should draw from this diatribe:
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1) Big computers that have millions of IC's in them perhaps should
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be left on.
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2) Small computers (PC's etc) It just won't matter.
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Note: Failures of mechanical parts are nothing like that of semiconductors!
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(You know, disk drives, switches, keyboards, fans, etc.)
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I wish I could provide references to all of what I have stated, but
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I can't easily. This is stuff that I have gleaned from years as an Engineer,
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and many many hours of college course work. So some settling may have
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occurred :-)
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Chuck Harris
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C.F. Harris - Consulting
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===============================================================================
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From: nicholso@hpcuha.HP.COM (Ron Nicholson)
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Subject: Re: Dusty Dorms. WAS: Re: Computer on 24hrs.day? (yes or no)
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Message-ID: <10350001@hpcuha.HP.COM>
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Date: 30 Mar 90 23:29:35 GMT
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gregk@ubvax.UB.Com (Greg Kendall) / 6:59 pm Mar 28, 1990 / writes:
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>I've heard a lot of claims about how it's "harder" on the PC to power
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>up than to leave it on. I have yet to hear of any real data on failure
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>rates. ...
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----------
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Long long ago, in a far away place, when I worked for a high volume
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computer manufacturer, I ran across some real statistics. Some
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experiments had been done on the difference in failure rates between
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continuous burn-in and power cycling. My dim recollection is that there
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was a significant increase in the infant mortality rate of the group
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that underwent power cycling.
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The sample size was large enough to be statistically convincing. The
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primary cause of the failures was due to thermal shock on solder joints,
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IC bonds, sockets and connectors.
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Alas I no longer have access to the details of that experiment. What I
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now do is to frequently power cycle new equipment (while it's still under
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warranty of course) to shake out the lemons, and to minimize power cycles
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thereafter. I still have seen no good data on electromechanical
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equipment, like disk drives.
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---
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Ronald H. Nicholson, Jr. Hewlett Packard
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uucp: nicholso@hpda.HP.COM Cupertino, CA
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===============================================================================
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From: dan@tinton.tinton.ccur.com
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Subject: Computer on 24hrs a day?
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Date: 5 Apr 90
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Power conditioning must play a part in the equation. If one's AC supply is
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relatively dirty and one has limited power conditioning equipment, then leaving
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one's system on constantly leaves it open to large power glitches wreaking
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havoc.
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===============================================================================
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From: uunet!tiamat!quintro!bpdsun1!rmf (Rob Finley)
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Subject: Re: Computer on 24hrs.day? (yes or no)
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Date: 15 Apr 90 06:38:02 GMT
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My floppy drive fails to read some disks when cold. So, I leave it
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on. After three years, the only thing that died is the cheap 12V fan
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in my UL listed power supply. $15 and a trip to Radio Shmuck did the
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trick. It's still ticking.
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Just be sure to use a good screen blanker program. Most of our machines
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at work are never turned off.
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But. My 386 at work ate two hard drives and three motherboards before
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they replaced the power supply. The +5v line ran at 5.2v while the
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other voltages were acceptable with low electrical noise. New supply
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and it works great.
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Before deciding whether to leave it on or not. Consider these points:
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Does your system draw air into the box through a vent on the back?
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If you feel air being blown out the vent on the power supply, then
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it is most likely sucking it in through the biggest hole: your
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floppy drive. When air comes in through the drive door, it drops the
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dust it was carrying all over your machine, mostly on your disk drive.
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Remedy: replace the power supply with one that has the fan going
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in the right direction. Swapping the Red and Black wires on it won't
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do. You will cause irrepairable damage to the solid-state controller
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(they don't have brushes like conventional DC motors to control noise).
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I had to open the power supply box (after removing it from my machine)
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unscrew the fan mounting hardware and turn it over so that it draws air
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in from the vent that sticks out the back of the cabinet when installed.
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With your fan now drawing air from one place, you can tape a piece of
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foam or air filter material over that vent to catch a large percentage
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of the dust before it gets inside. But, you must check the filter
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regularly. The entire system may be at risk with a blocked air filter.
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Or, if anything, your expansion boards will attract the dust before it
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reaches your floppy drives. Unfortunately, too much dust on the
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motherboard or expansion boards will insulate the chips and prevent
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them from keeping cool.
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If you have large expansion boards or full height hard drives,
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look into adding additional fans. Some cabinets allow you to have a
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second one on the front end of the expansion card cage. If you don't
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want to open your machine and it overheats or attracts dust in all
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the wrong places, turn it off if possible. Machines today are durable.
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Safety warning. If you don't feel comfortable opening your machine,
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find someone who is. If your dealer doesn't feel comfortable, find
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another dealer. The one you have now probably can't fix it if it dies.
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The power supply circuit can still hold a charge when it is unplugged.
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You shouldn't have to touch any of the circuits on the power supply
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board. You aren't rewiring it, you're flipping the fan over and putting
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the screws back in.
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That wasn't hard. Was it?
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-----
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quintro!bpdsun1!rmf@lll-winken.llnl.gov uunet!tiamat!quintro!bpdsun1!rmf
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===============================================================================
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From: kabra437@pallas.athenanet.com (Ken Abrams)
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Subject: leaving PC on
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Date: 8 Aug 90
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In article <hart.650028982@blackjack> hart@blackjack.dt.navy.mil (Michael Hart) writes:
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>I refer you to the "light bulb law". That law being: When do light bulbs
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>burn out?? _when you turn them on_ There is a large surge of current through
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Even though most of the components in a PC are NOT light bulbs ( and don't
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behave like one either), I would agree with you that leaving it on is best
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if the ONLY consideration was hardware reliability (and it is connected to
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a stable power source). As I see it, however, hardware reliability is not
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the only issue and a case can be made for the theory that a properly designed
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disk drive will wear out from heat and friction and dirt before it will
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suffer any electrical damage from being started and stopped once a day.
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I think that all the energy wasted by millions of PCs left on 128 hours a
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week when they are not being used is a bigger and more important issue than
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whether or not it will extend your repair cycle from 3 years to 5 years.
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There is also a small extra potential for a fire in a running device.
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I have been in the computer industry for close to 25 years, mostly as a
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technician. I have weighed all the arguments and I have decided to turn
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MY machines off when they will not be needed for 6 hours or more. I even
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turn the Xenix box off over the weekends.
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Like a lot of other things in modern life, this is not strictly a technical
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call but it has some moral undertones too. Make your own call but don't
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overlook part of the factors in the process.
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===============================================================================
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From: linderd@merrimack.edu (Doug Linder)
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Newsgroups: comp.sys.ibm.pc
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Subject: Re: Horizontal cards (was Re: Standing your box upright)
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Message-ID: <18991.262c5b5c@merrimack.edu>
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Date: 18 Apr 90 12:19:40 GMT
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In article <1990Apr16.181035.3017@seri.gov>, marshall@wind55.seri.gov (Marshall L. Buhl) writes:
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> Another thing to consider when standing a PC on end. One of my secretaries
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> stood hers on end for a year or so. When she left, I tore the machine
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> apart and found that the AST 6 Pack was really warped. If you laid it on
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> a table, one end would be 1" in the air. It still works, but...
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Maybe the solution is to flip the thing from end to end every 6 months to
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even out warpage? ;-)
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But seriously, folks, when I was a PC tech I did see some problems with this.
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Essentially, it seems that the larger the number of cards you have, how big the
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cards themselves are (height/thickness) and how good your fan is are the big
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factors. Remember, these cards are designed to stand on edge and let the heat
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float to the top of the box where it can be sucked away by the fan. A PC on
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its side screws up this system and the heat, trying to rise, gets caught by the
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cards and what you end up with are little heat sandwiches between the cards -
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the hot air has nowhere to go. I have seen machines with lots of big cards in
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them that you could fry an egg on. The biggest danger with cards "melting" is
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not only that the card itself may malfunction, but that it wil come in contact
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with something it shouldn't (usually another card, the one below it) and short
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out the whole works. I have seen motherboards die this way.
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This can be alleviated by some things such as:
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1) a fan (a standard room fan pointing at the machine),
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2) room A/C,
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3) simply leaving the cover off the machine and covering it with a cloth
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supported by a wire frame (to hold the cloth away from the machine a
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few inches)
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4) If the cards are long enough, mounting brackets at the front of the machine
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for the ends of long cards to rest in will prevent "drooping" at the ends
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but alas, cards still droop in the middle.
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My best advice: Unless you have only a monochrome card and a serial/parallel
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card, or some other very low heat/high circulation setup inside the machine,
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place it the way it was designed to be placed - "power users" take note. The
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equipment is too expensive and your time too valuable to waste with breakdowns.
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Would you want your PC to die in the middle of a presentation because the
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Video card just warped enough to touch the drive controller and short out the
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whole works? BTW, though, I have found that smart terminals like Novell
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network PCs work OK on end - as long as the novell card is about the only thing
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in the machine.
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Hope this helps.
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--
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Douglas D. Linder linderd@merrimack.edu
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Merrimack College, N. Andover, MA {uunet,wang,ulowell}!samsung!hubdub!linderd
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===============================================================================
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From: alz@tc.fluke.COM (Al Weiss)
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Subject: Is it [orientation] harmful to disk drives?
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Date: 4 May 90
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Dunno about floppies. For hard drives it depends upon the manufacturer. All of
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the Seagate manuals I've seen, for instance, are VERY specific in their manuals
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about not elevating the front or back more than 5 degrees from horizontal.
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They can however be turned on their sides up to 90 degrees, but no further (ie
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not upside down). They should also be formatted in their permanent
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orientation. My understanding is that the head positioning mechanism gets worn
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out on an angle, and the motor bearings can't hack being upside down. On the
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phone, Seagate told me that they would not honor any warrantee if they know
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that it has exceeded those limits. I've heard some newer Seagates don't have
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limits, but don't know for sure, nor do I know about the CDC's. Conner,
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Quantum, Miniscribe, Maxtor(?), on the other hand, (of the ones I've seen)
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specifically say "any orientation".
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===============================================================================
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