Help Plz... it wont start

[AlecJ32]

Re: Help Plz... it wont start

When you do hold the power button down without the PSU connected it completes the circuit and drains the capacitors which means the cmos has no power to keep the bios preferences stored on it.

....Which would work if the PC got it's power from the capacitors on the CMOS chip. However, it doesn't, so that wouldn't work. The battery is used to store data on CMOS until the stage in the Power On Self Test in which the CMOS data is retrieved from the chip occurs. Trying to turn on the PC with no power connected would not effect CMOS, since that stage in the POST would not be reached without external power.

Also im pretty sure PSUs send some voltage down the 3 and/or 5v rails even when switched off as most mobos have an LED which stays lit even when the comp is switched off.

Yes, but the power supply is not running fully until it receives the power-on signal from the motherboard.

[Busby, Paul (Bicci)]

Re: Help Plz... it wont start

....Which would work if the PC got it's power from the capacitors on the CMOS chip. However, it doesn't, so that wouldn't work. The battery is used to store data on CMOS until the stage in the Power On Self Test in which the CMOS data is retrieved from the chip occurs. Trying to turn on the PC with no power connected would not effect CMOS, since that stage in the POST would not be reached without external power.

Yeeeaaaah but we are talking here with the assumption that you have taken the battery out

Also an easier way to clear CMOS, this should work I do this if mine doesnt boot as the CLR CMOS jumper is under my gfx card, all you gotsa do is turn off PC, unplug power supply, remove the battery and hold down the power button for 10 secs, then put battery back in and plug in and start up...

So the CMOS isnt getting power from the battery or the PSU.... how is it retaining data for 10-15 minutes, an hour or whatever it is? Yes thats right its mr capacitor :p

Yes, but the power supply is not running fully until it receives the power-on signal from the motherboard.

CMOS is definately not something which draws from the 12v line

[AlecJ32]

Re: Help Plz... it wont start

Yeeeaaaah but we are talking here with the assumption that you have taken the battery out

.....So taking the battery out suddenly changes the PCB traces on the motherboard, so that now when you try to power on your PC it gets its power from the Capacitors on the CMOS chip, huh? Yeah, you're making a lot of sense. Taking the battery out isn't going to change the power configuration of the CPU.

So the CMOS isnt getting power from the battery or the PSU.... how is it retaining data for 10-15 minutes, an hour or whatever it is? Yes thats right its mr capacitor :p

....And there are millions of capacitors in a PC. Your RAM, for example, has one capacitor for every bit of data it can store, and those capacitors have to be refreshed constantly or all data stored on the DRAM will be lost. The ones used by CMOS are not used for providing power to anything but CMOS, and aren't used for powering on your PC, so trying to power on your computer with no power and no CMOS battery isn't going to do anything to them. By your theory, trying to power on your PC with no power and with the battery in would cause it to drain the CMOS battery.

CMOS is definately not something which draws from the 12v line

Sure, but what does that have to do with anything?

[Busby, Paul (Bicci)]

Re: Help Plz... it wont start

.....So taking the battery out suddenly changes the PCB traces on the motherboard, so that now when you try to power on your PC it gets its power from the Capacitors on the CMOS chip, huh? Yeah, you're making a lot of sense. Taking the battery out isn't going to change the power configuration of the CPU.

Whats the CPU got to do with it? I never said it takes power from the capacitors ON the cmos chip.
The cmos chip only uses the battery when the PC is switched off, when its switched on it takes power from from PSU. PSUs also have a lot of capacitors in them which are used, along with a number of other componants, to convert the AC mains supply (whatever it is in your area) into various DC voltages, ensure stability etc etc... and just like any other capacitors they store electricity for a certain amount of time. The mothetherboard MAY also have a number of capacitors inbetween the 24pin connector and the cmos chip... we are ok so far yes?
If you take out the battery and press the power button it is going to try and take power from the PSU which will draw the remaining power from the various capacitors connected to it draining them meaning there is nothing to keep the cmos going and it clears your settings... how can you argue with this?

....And there are millions of capacitors in a PC. Your RAM, for example, has one capacitor for every bit of data it can store, and those capacitors have to be refreshed constantly or all data stored on the DRAM will be lost. The ones used by CMOS are not used for providing power to anything but CMOS, and aren't used for powering on your PC, so trying to power on your computer with no power and no CMOS battery isn't going to do anything to them. By your theory, trying to power on your PC with no power and with the battery in would cause it to drain the CMOS battery.

My theory doesnt dictate that at all. If you press the power button with the battery in it will drain the capacitors still just not wipe the cmos because it will still get power from the battery. Where on earth did i say the battery was connected to booting up the PC?

Sure, but what does that have to do with anything?

Seeing as we have established there is either 3 or 5v power going to the motherboard still, what im not sure of is wether power goes from the PSU to the CMOS chip when your PC is turned off but still plugged in or if it always draws from the battery when it is switched off. You stated the PSU isnt fully working till its powered up, yes i know but the main thing which gets powered up will be the 12V rails and the cmos wont need them.

[AlecJ32]

Re: Help Plz... it wont start

Whats the CPU got to do with it?

A lot. It handles the initial responsibility of starting the PC. When you power on your PC, the motherboard sends an activate signal to the power supply, which sends 12v power to the CPU, which starts the BIOS and loads data from CMOS.

I never said it takes power from the capacitors ON the cmos chip.

Then how will those capacitors be drained by trying to turn the PC on?

The cmos chip only uses the battery when the PC is switched off, when its switched on it takes power from from PSU. PSUs also have a lot of capacitors in them which are used, along with a number of other componants, to convert the AC mains supply (whatever it is in your area) into various DC voltages, ensure stability etc etc... and just like any other capacitors they store electricity for a certain amount of time.

Yet you'll notice, when you unplug your PSU from the wall, the light on your motherboard doesn't stay on. If it were supplying power to CMOS from the capacitors, wouldn't it also supply power to the motherboard light?

The mothetherboard MAY also have a number of capacitors inbetween the 24pin connector and the cmos chip... we are ok so far yes?
If you take out the battery and press the power button it is going to try and take power from the PSU which will draw the remaining power from the various capacitors connected to it draining them meaning there is nothing to keep the cmos going and it clears your settings... how can you argue with this?

The function of those capacitors is not to supply start-up power, though, so the motherboard isn't going to try and draw power from them in order to start up.

My theory doesnt dictate that at all. If you press the power button with the battery in it will drain the capacitors still just not wipe the cmos because it will still get power from the battery. Where on earth did i say the battery was connected to booting up the PC?

Because your theory suggests that if there is no power being provided from the power supply, it will attempt to draw power from the same circuit from which the CMOS chip gets it's power.

Seeing as we have established there is either 3 or 5v power going to the motherboard still, what im not sure of is wether power goes from the PSU to the CMOS chip when your PC is turned off but still plugged in or if it always draws from the battery when it is switched off. You stated the PSU isnt fully working till its powered up, yes i know but the main thing which gets powered up will be the 12V rails and the cmos wont need them.

The power supply may or may not supply power to CMOS while plugged into the wall. However, when the PSU isn't plugged in, it's not going to provide power. You can observe this by watching the lights on your motherboard. When your PC is plugged in, they turn on. When it's unplugged, they shut off, so I'm fairly certain the capacitors aren't supplying power to CMOS, either.

[Busby, Paul (Bicci)]

Re: Help Plz... it wont start

A lot. It handles the initial responsibility of starting the PC. When you power on your PC, the motherboard sends an activate signal to the power supply, which sends 12v power to the CPU, which starts the BIOS and loads data from CMOS.

and that tells us what to do with what we are talking about? Just because the CPU intructs the bios to load the data doesnt mean it has anything to do with power going to the CMOS. If the CPU did have anything to do with the controlling of power to CMOS then it would flash everytime you turned your PC off.

Then how will those capacitors be drained by trying to turn the PC on?

Sorry i maybe should have worded more carefully... i meant 'I never said it takes power from ONLY THE capacitors ON the cmos chip.

Yet you'll notice, when you unplug your PSU from the wall, the light on your motherboard doesn't stay on. If it were supplying power to CMOS from the capacitors, wouldn't it also supply power to the motherboard light?

But does it go off straight away or does it take a min or two? i know mine take a while before the light goes off suggesting there is power stored in a capacitor somewhere still supplying it.

The function of those capacitors is not to supply start-up power, though, so the motherboard isn't going to try and draw power from them in order to start up.

We are not supplying power to the 'motherbaord' we are supplying it to the CMOS chip which is only a very very small part of the motherboard which uses a very very small amount of power to work nothing like what is needed for start up. Besides which, the capacitors do actually get drawn from when you are booting up as the power goes through them before the load.

Because your theory suggests that if there is no power being provided from the power supply, it will attempt to draw power from the same circuit from which the CMOS chip gets it's power.

no it doesnt.... My theory in no way suggests booting up relys on power to the cmos and nowhere did i say that. What im saying is that when you press the power plug it trys to draw power from the psu (which is does) then when you switch it off it draws power from the battery (which is does) I dont know for sure but i would take a guess that a very simple logic/switching circuit (that also runs off the battery) detects if there is any voltage coming from the PSU and if it isnt then it draws from the battery.

The power supply may or may not supply power to CMOS while plugged into the wall. However, when the PSU isn't plugged in, it's not going to provide power. You can observe this by watching the lights on your motherboard. When your PC is plugged in, they turn on. When it's unplugged, they shut off, so I'm fairly certain the capacitors aren't supplying power to CMOS, either.

Well then explain to us why the CMOS take so long to clear after you have removed the battery and disconnected the PSU? Where exactly does it get its power to stay alive from? 10-15 minutes in my system and Alex is suggesting maybe an hour of so for his you going to tell me the tiny capcitors in the chip itself have enough power for that long? I find it funny that there is big capacitor right next to the battery on my dads mobo :/

[AlecJ32]

Re: Help Plz... it wont start

and that tells us what to do with what we are talking about? Just because the CPU intructs the bios to load the data doesnt mean it has anything to do with power going to the CMOS. If the CPU did have anything to do with the controlling of power to CMOS then it would flash everytime you turned your PC off.

I don't know any other way to say "The CPU is the first component to start when you try and power on your PC, not CMOS." If there's no power, the PC won't make it as far as CMOS, so CMOS won't be affected by the button-press.

But does it go off straight away or does it take a min or two? i know mine take a while before the light goes off suggesting there is power stored in a capacitor somewhere still supplying it.

On all the PCs I've worked with, it shuts off within 3-5 seconds of removing power from the motherboard.

We are not supplying power to the 'motherbaord' we are supplying it to the CMOS chip which is only a very very small part of the motherboard which uses a very very small amount of power to work nothing like what is needed for start up

You aren't supplying it directly to CMOS. You're supplying it to the motherboard, which supplies it to CMOS.

Well then explain to us why the CMOS take so long to clear after you have removed the battery and disconnected the PSU? Where exactly does it get its power to stay alive from? 10-15 minutes in my system and Alex is suggesting maybe an hour of so for his you going to tell me the tiny capcitors in the chip itself have enough power for that long?

Perhaps.

[Busby, Paul (Bicci)]

Re: Help Plz... it wont start

I don't know any other way to say "The CPU is the first component to start when you try and power on your PC, not CMOS." If there's no power, the PC won't make it as far as CMOS, so CMOS won't be affected by the button-press.

The logic which switches the CMOS from battery to mains has to be a self contained otherwise it wouldnt work... so it has nothing to do with the CPU. The only way the CPU would be involved was if it sensed if there was power going to the CPU but whats the point in that? if you pull yur cpu out your computr will still try and switch on it will just beep at you instead of posting - you think the CMOS is still running from battery at this point because i certainly dont.

On all the PCs I've worked with, it shuts off within 3-5 seconds of removing power from the motherboard.

But not instantly...? suggesting there is still power being supplied to them for a short while yes? comes from...? Pixie dust yes?

You aren't supplying it directly to CMOS. You're supplying it to the motherboard, which supplies it to CMOS.

Surely your saying here - inbetween the CMOS and the 24pin plug with the 3v line which i assume is the one for CMOS, there is a number of componants... like capacitors? To be honest im reckoning in most mobos the power goes pretty much straight from the PSU to CMOS but your way works in my favour too so whatever.

Perhaps.

are you serious? :hmm:

[[Expletive Deleted]]

Re: Help Plz... it wont start

Now someone question the other man's parental lineage! Question the legality of his mother's profession! Oh, and say he has no father!

[AlecJ32]

Re: Help Plz... it wont start

The logic which switches the CMOS from battery to mains has to be a self contained otherwise it wouldnt work... so it has nothing to do with the CPU.

That doesn't mean that CMOS switches power sources before anything else happens.

The only way the CPU would be involved was if it sensed if there was power going to the CPU but whats the point in that? if you pull yur cpu out your computr will still try and switch on it will just beep at you instead of posting - you think the CMOS is still running from battery at this point because i certainly dont.

Probably not, but there certainly isn't anything else happening to it, either. Either way, that's not the situation in question.

But not instantly...? suggesting there is still power being supplied to them for a short while yes? comes from...? Pixie dust yes?

It could be capacitors in the power supply, or it could be capacitors on the motherboard. Either way, it'd be irrelevant, since they don't stay on for the 15 minutes you're claiming it takes to

Surely your saying here - inbetween the CMOS and the 24pin plug with the 3v line which i assume is the one for CMOS, there is a number of componants... like capacitors? To be honest im reckoning in most mobos the power goes pretty much straight from the PSU to CMOS but your way works in my favour too so whatever.

At this point, we're going in circles, since we've already been over this.

are you serious? :hmm:

If I wasn't, wouldn't I have made it a bit more obvious that I wasn't?

[Busby, Paul (Bicci)]

Re: Help Plz... it wont start

Now someone question the other man's parental lineage! Question the legality of his mother's profession! Oh, and say he has no father!

:laugh: good point, im out...