Solved computer forced shutdown safe or not

November 15, 2010 at 01:41:37
Specs: Windows XP

Hi,
Just generally when you computer is hung up ,cntrl alt del doesn't work nothing works, is a forced shutdown using the power button better than pulling out the battery or is it effectively the same thing,
Cheers,
G

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✔ Best Answer
November 16, 2010 at 02:43:42
Sudden removal of power from a hard disk will not cause damage.

The only damage that could be caused is the the head will crash into the disk surface and scratch it. Under normal circumstance the head is kept from hitting the disk by what is known as the Bernoulli Effect. This causes the spinning disk to create a high pressure area on its surface which the disk head cannot get through and it effectively floats on a cushion of air. This cushion of air is about five microns thick which is about half the thickness of a human hair.

When power is removed the disk stops spinning, but it doesn't stop immediately. There is enough time for the head to be moved to the outside of the disk in a blank area called the landing zone. When the disk has slowed down sufficiently the head will settle on this landing zone without causing any damage.

In the early days when hard disks where relatively new the drive head was controlled by a stepper motor. This created the problem that if power was suddenly remove the head would crash into the hard disk at the place it was damaging data. During a normal shut down procedure the hard was "parked" over the landing zone before power was removed. A sudden loss of power and this could not happen as a stepper motor needs power to do anything.

This led to the introduction of the voice coil to control the heads. It is called a voice coil because it behaves in a similar way to the coil in a loudspeaker which is just a solenoid. When power is removed the solenoid reverts to its rest position which moves the head over the landing zone. It was now possible to move the head without the need for power and one big problem was solved.

Pressing and holding the power button for four seconds by passes the shutdown procedure which is
under software control, and simply removes power from the power supply. Pretty much the same as pulling the plug except that is saves groveling around the back of the computer.

Stuart



#1
November 15, 2010 at 04:49:04
The safest way is to hold the power button in till it shuts off safely. Removing the battery could possibly jolt the MOB and cause damages. Others may differ on this ;-)

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#2
November 15, 2010 at 14:58:49
Power button crashes the hardware. Safest to shut down with the button as already given.

Might be worth saying what you are trying to do when it freezes, maybe we can help stop it doing so.

How to know you are getting old 2:
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#3
November 16, 2010 at 01:47:12

I am unclear what the power button does. Does it actually stop the disk in acontrolled manner before powering off which would be safe, not bothered about anthing else, or does it just cut the power directly after 5 seconds which is the same as pulling the plug directly never seen it written anywhere what the power button actually does. In unix there are fast shutdown routines which will sync disks so its safe even if its not a full shutdown

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Related Solutions

#4
November 16, 2010 at 02:43:42
✔ Best Answer
Sudden removal of power from a hard disk will not cause damage.

The only damage that could be caused is the the head will crash into the disk surface and scratch it. Under normal circumstance the head is kept from hitting the disk by what is known as the Bernoulli Effect. This causes the spinning disk to create a high pressure area on its surface which the disk head cannot get through and it effectively floats on a cushion of air. This cushion of air is about five microns thick which is about half the thickness of a human hair.

When power is removed the disk stops spinning, but it doesn't stop immediately. There is enough time for the head to be moved to the outside of the disk in a blank area called the landing zone. When the disk has slowed down sufficiently the head will settle on this landing zone without causing any damage.

In the early days when hard disks where relatively new the drive head was controlled by a stepper motor. This created the problem that if power was suddenly remove the head would crash into the hard disk at the place it was damaging data. During a normal shut down procedure the hard was "parked" over the landing zone before power was removed. A sudden loss of power and this could not happen as a stepper motor needs power to do anything.

This led to the introduction of the voice coil to control the heads. It is called a voice coil because it behaves in a similar way to the coil in a loudspeaker which is just a solenoid. When power is removed the solenoid reverts to its rest position which moves the head over the landing zone. It was now possible to move the head without the need for power and one big problem was solved.

Pressing and holding the power button for four seconds by passes the shutdown procedure which is
under software control, and simply removes power from the power supply. Pretty much the same as pulling the plug except that is saves groveling around the back of the computer.

Stuart


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#5
November 16, 2010 at 22:52:25
Stuart,
thanks I'll feel safer pulling the plug in future which we all have to do occasionally,

Cheers,
Grahame


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#6
November 17, 2010 at 06:57:58
LOL...have fun pulling the plug, then you can post another hardware problem ;-)

Some HELP in posting on Computing.net plus free progs and instructions Cheers


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#7
November 17, 2010 at 07:39:47
XpUser4Real:

Can you give me an explanation as to how the lack of electricity can damage hardware. I can tell you how too much can damage hardware but if non at all can damage hardware I would be very interested in finding out. There has to be a reason if you are so insistent it can happen.

A simple explanation will do but a technical explanation will be just as welcome as I do understand the relationship between Volts, Amps and Resistance.

Stuart


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#8
November 17, 2010 at 07:51:01
StuartS

Lack of electricity can obviously do no damage in its own right. However the spike caused by arcing that you get get from pulling the plug could possibly do so. A switch is designed to break the circuit cleanly and quickly, with minimal arcing within it. Pulling the plug is much more dependant upon how you do so, hence the likelyhood of arcing is greater.

Further, when waggling the plug to pull it out there is a possibility of the connection momentarily going off then on again - best avoided in my view.

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You start converting your age to hexadecimal


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#9
November 17, 2010 at 07:52:42
I only speak from experience of problems I have seen caused when yanking a plug out of a PC. There have been many...I have no other explanation. Common sense says to shut down the PC properly without causing damage is to hold in the power button till it shuts down safely.

Some HELP in posting on Computing.net plus free progs and instructions Cheers


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#10
November 19, 2010 at 00:00:01

Hi,
the last comment takes back to the beginning the assumption that pressing the power button is a safe shutdown is only an assumption. Personally I have never actually pulled the plug but used the power button but aside from the agrgument about the disk spinning down which I didn't know I have never seen or heard an explanation on what software/procedure if any is employed when you hold down the power button and how that differs from a standard shutdown, and if not it is the same as pulling the plug

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#11
November 19, 2010 at 06:10:28
Holding down the power button reverses the process that occurs when you press it to start the computer, it breaks the connection between the green and earth from the power supply. The green must be earthed for the power supply to run. When the power button is pressed and held, this connection is reversed and the power supply stops and the computer goes of. It is this process that allows a computer to boot up normally after a power failure when power is restored without any user intervention. This is controlled by a setting in the BIOS but not all BIOS implement it. The green and black is connected as soon as power is applied. A useful facility for an unattended server.

During a normal shutdown the Operation System goes through its shutdown procedures, closing files, stopping services, flushing buffers, etc. When the OS is finished it tells the BIOS which then opens the green cable and the computer turns off. So pressing the start button for four second, the computer ends up doing the same as a normal shutdown except that it by-passes the software part and goes straight to the hardware via the BIOS and Motherboard. The only software involved is in the BIOS.

When the power supply is off this green and black wire is open circuit. When the power button is pressed, an electronic switch in the main chips-set closes the circuit and the power supply starts up. They Grey power-good signal then comes into play. This is controlled by the power supply and is at Ov at start up. While the power good signal is at Ov minimal power is sent to the motherboard and an NMI to the CPU which effectively stops the CPU from doing anything.

When the power supply has stabilized the power good signal is raised to 5v, full power is applied, the NMI is removed and the boot up proceeds. This process usually takes about half a second but for a CPU the can execute millions if not billions of instruction in half a second, it is a very long time. If during normal operation the power supply detects any anomalies in the power, it lowers the power-good and stops the computer. If this anomaly is short lived, less the second, a spontaneous reset occurs. This what happens when a power supply is overloaded and the voltages begins to drop. As soon as the CPU is stopped, the overload is removed and the computer continues, until the next time.

However is the anomaly lasts longer, such as a gross over voltage, The power supply shuts down via the green cable, all under the control of the chip-set.

Some cheep power supplies to don't properly implement this power good signal and holds it permanently at 5v. This is why a cheap power supply can destroy the motherboard in the event of a power supply fault. There are other safety devices built into power supplies as well that prevent bad power getting to the motherboard. Cheap power supplies don't implement them all.

Good quality power supplies have an electronic fuze that will trip if anything untoward happens. It acts a bit like a RCB. The only way to reset this fuze is to remove all power which means pulling the plug, waiting a few seconds and starting all over again, but with an undamaged motherboard.

It is for this reason that I don't believe and spikes caused the arcing from pulling the plug will cause any damage, except in a cheap power supply where non of the safety devices are implemented. Probably why I have never experienced the problem as I have always used good quality power supplies.

Stuart


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#12
November 19, 2010 at 07:51:06
I don't dispute the power supply principles aired. However, it still true to say that with any electrical appliance (computer or other), switches are designed and intended to break circuits cleanly with minimal or no arcing. Mechanical types have an inbuilt avalanche effect whereby at a certain point the switch will toggle over under the control of a spring. This defines the cleanness of the break and is out of the control of the operative. They also have specified clearances between the open contacts that further reduce the likelihood of an excessive arc being drawn. Solid state switches, although obviously entirely different, still achieve the same overall objectives, which are basic facets of switch design.

I have definitely run into computer and monitor plugs and sockets that have burn marks on their pins caused by arcing, which can only have happened if they were pulled while the current was flowing. The arc is drawn because it is uncontrolled and just a matter of how neatly the operative withdraws it. It seems pretty straightforward to me, you power off with the switch "before" removing the plug, which is good sensible practice for the reasons given.

I shall leave it at that because I'm starting to repeat myself. If what I have said is not clear enough then search Google - it's bound to all be out there somewhere.

EDIT: Found this for starters:
http://www.allaboutcircuits.com/vol...

How to know you are getting old 3:
You start converting your age to hexadecimal


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#13
December 10, 2010 at 09:32:03
Hello. Recently I forced a shutdown with the power button and the computer wont start after that, no fans spinning. The only indication of power is the mobo led. My guess is a psu faillure or could it be the motherboard? I tryed to remove the components one by one to see if any was causing this but it doesn't turn on, tested with only the board and psu connected but without luck.

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#14
December 10, 2010 at 12:26:43
zilaan

Unfortunately, although not it is not entirely impossible to find and replace components on a mobo it is pretty near so. There is little real information available in order to make any more than a vague diagnosis or guess. Even if you are certain you have found the defective components it is often very difficult to replace them when forced, due to space, to use a very small soldering iron. This is because boards are often multilayered and you cannot get the heat in the all right places at a given time to remove them and you could put faults on when attempting to fit a new one. You often need more heat than is available from a small iron due to heat sink affects on the board.

Boards are put together using solder bath techniques which are therefore not within the scope of even the most experienced DIY person. The only hope is that you can cut the existing component away leaving the legs in postion, in order to solder the new part onto them. Even doing that has its pitfalls because undue lead length can affect results due to the high speeds involved inside a computer. Mostly mobo replacement is the only way forward.

We all live on a ball.


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#15
January 17, 2011 at 18:24:16
Thanks for your detailed and well written explanation Post#11. I can say I have learnt something new today. Keep up the good work.:-)

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#16
January 17, 2011 at 18:37:44
Hi,
I know that an app/software leaves "junk files" on your pc until you close them down, then the junk files are deleted by the app/software running them. If the power is turn off due to power cut before the app can shut down and clear the junk files, they get left on you pc, until you clean it using a cleaning software program. If you keep stopping the power, the junk files will build up over time using hard drive space up.
So why it will not damage the hard drive or the software running, it will eat away at your free space. (RevoUninstaller is great for removing junk files.)

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#17
January 17, 2011 at 18:57:55
Although the power supply is a good buffer there is still the possibility that if you pull the plug while a computer is running it will cause a large enough spike to get through. This could corrupt the software.

It is sensible, whatever the pro's and con's, to use Windows software to shut down the machine first, then unplug.

I can't see why anyone would think it better to just unplug. The only time you would need do this is if Windows is not available, in which case the next best option is to first use the switch.

We all live on a ball.


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