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help resolve debate: is pulling comp plug same (electrically) as reset button?

T

TheWart

Diamond Member
my roomate and i got into an argument over whether it is worse for someone (say if comp hangs on shutdown) to hit reset switch or just pull the plug (literally) on the back of the psu. neither of us are electrical engineering majors, but i have heard from technicians that pulling plug is bad, and my mobo manual says not to do it (i think). my roomate contends that there is no difference. please help us resolve this, as technical as you wish, and possible websites/literature in support of what you say (not necessary, but would be appreciated).

thx, i know AT can always help.
 
You are correct pulling the plug on the back of a computer is not good for it.
The reason I am not for sure of. I can think of a few things that could cause damage. Like a electrical spike and so on. And the sudden lose of power isnt good either.
A reset does not just cut power it is controlled (or I think).
The ATX board/psu are reset and shut off though the mobo. There is no mechanical switch like the at boards/psu had.

I would think that you mobo saying that it is not good would be enough to prove your point. They would not put something like that in it unless it could cause damage.
 
Obviously there is a difference because every pc I've ever hit the reset button on keeps the fans going and LEDs lit when you press and hold the reset button. The question is would be is it bad to pull the plug. The answer is "not really" if you have a good power supply.

I don't know the really technical details, but here my best attempt in Turkey-mangled language (and someone correct me if I'm wrong): typically damage in an IC is caused by over-spec current thru the part or over-spec voltage across the part. So to prevent damage to your PC parts, all you have to do is prevent these conditions. Good power supplies are designed so that reasonable fluctuations in input (from the wall) power still results in in-spec output voltage. They are also designed so that power stays in-spec for some common situations, like the power supply turning on, turning off, waking up, and pulling the plug. This may even be part of the ATX spec - how long a power supply must provide power after the plug has been pulled/power goes out, maximum peak voltage when the plug is pulled, maximum current when the plug is pulled, etc. So it won't do any real harm... but it's probably best to stay away from pulling the plug anyway.
 
pulling the plug is worse.

when you hit the power button it just doesn't power up the CPU or mobo but there is still power flowing through the power supply

it's not very bad per say but it's always better to keep things at a constant rate, keep a little bit of power flowing at all times instead of running that destructive jolt the second something gets power. it ties into that saying that turning a light bulb on takes 10x as much power as when it is running at a constant rate
 
When you just yank the plug out, there is no time for the heads in the hard drive to get to their "landing zone" ( the place the heads go when power is turned off ) if you pull the plug you can crash the heads into your data = dead hard drive.

There are other things it does, but those are minor compaired to above.

<edit>
Oh, and I will take sleep and fun please.
</edit>
 
most modern hard drives will use the inertia of their rotation to park the heads though, so I don't think that would be much of an issue.
 
yeah, its pretty cool. i wonder about laptop drives though, cause every one i've carried clicks if you tilt it back and forth :Q
 
The reset button sends a reset signal to all of the components telling them to go into reset mode but the power supply continues to supply power to the system. Signalling reset causes a number of things to happen and most of the system components enter into a self-test mode for a period of micro to milliseconds. Pulling the plug removes all power to the system leading to the power supply signalling shut-down. In a well-designed system neither should cause permanent harm the system, but both can lead to data loss since there isn't enough time to flush the disk caches, or write 'dirty' data on the CPU (ie. data that has been changed) back to the disk.
 
I'm tempted to say it is worse because, unless you are really swift in yanking the sucker out of the socket, there could be a time in which the leads disconnect and reconnect rapidly, which could cause a power spike to the system. I don't know for sure, but it is kinda like flickering a light bulb on and off repeatedly. It will cause the bulb to burn out faster than if you just left it on all the time. I don't know if ATX PS's would do this though, as they are software controlled, not like AT PS's where they are hardware/switch controlled.
 
Better than pulling the plug, but more effective than a reset. Press the power button. Any decent power button should have an anti-bounce circuit. (Forget what it is called, but basically a flip-flop I belive). So you avoid the issues of spikes, while ensuring that most component receive a hard boot. Remember than on an ATX board, some components will sill have power wven when turned off.

If I run into issues with devices, I always power down and try again. I remember too many issues back in the DOS days when hitting the reset just didn't cut it. In fact I at one point I was unable to connect to our LAN straight after a boot. I had to boot up, reset and boot again. The initial boot set up the NIC, but there was an address conflict. The second boot used the new address of the NIC, and so whichever card/device it was conflicting with used another address and the conflict dissapeared!

As said, most PS should handle spikes from yanking the power out. You might reduce your MTBF slowly each time you do it. If you are on a power strip, hit the on/off button on that. You'll turn off with a cleaner signal.
 
Beau 6183,

I am also curious about the sudden disconnect/reconnect possibilty. I have to do a small amount of tech support at my job (teacher for adult ed), and I was recently called to another site. The user was having trouble printing, so she went to "check" all the connections at the back of the computer, starting with wiggling the power connector. Apparently, sparks resulted, she flipped off the power bar switch, and I was called. Result: dead mobo, dead power supply, dead cpu, dead HD.

I told her that although what she did was not a really good idea, and was absolutely not going to help her print, it still should not have done that. Partly to make her feel better for killing the system, and partly because I was not sure why it did it myself.

Anyone out there know of a reason why what she did would kill?

 


<< Poor quality ps >>

Most likely, but that doesn't justify pulling the plug out of the back of your PS as a common practice.
 
well I would say resetting the computer is better than pulling the plug because instead of the sudden lose of power to the units on the mobo / all your other devices on the computer, they are still in a continuous cycle- thus hitting reset just keeps the cycles going without the surge of power when you "plug" your computer back in and turn it on.

But that's my brief 'off the top of my head' reply. 🙂
-Dave
 
The reset button simply sends a hardware message via the motherboard to restart the post process and reboot the computer, pulling the plug actually shuts down the power supply. Now I know that there is a lot of debate as to whether you should leave your computer on all the time or shut it down and there are valid arguments for both. I would highly recommend hitting the reset above pulling the plug. Think of how much of a jolt of electricity your power supply receives every time you plug it in. Not to mention the fraction of a second it takes to regulate the power for the motherboard. Others argue that by cutting off the power it allows the solder on the board to expand/contract and therefore loosen connections. Others say that with air constantly flowing through the case, particulates are constantly damaging your hardware.....but I digress....

just tell your friend stay the @#$! away from your computer unless he hits the reset button...that's what it is there for.
 
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