Does The BIOS on a Motherboard "Turn it on" when the power switch is pressed?

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Roberto Bustos

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I have a gigabyte GA-EP45-UD3R motherboard that will only turn on when the green wire on the power supply is jumper'ed to ground. Well.. I have to clear the cmos first, then jumper the wires and she boots. I have to clear every time I boot, btw. Once shut down, the motherboard will not boot if I don't clear the CMOS. I have updated the BIOS to the latest firmware several times while booted and loaded defaults, but it does not help. And shorting the power pins on the motherboard does nothing.

Because of this I am sure it is a chip problem. But I don't know which chip triggers the motherboard to turn on and stay on (a relay of sorts?). The motherboard has 2 bios chips, so I am not sure if 1 would cause the other to fail too..?

Thanks for your time.

Robert
 
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Pinhedd

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That's very odd. The firmware itself (BIOS/UEFI) kicks in after the PC has been powered on but many motherboards have other special purpose devices onboard to manage things such as power. It's possible that there's a fault elsewhere in the mainboard, or the PSU itself.

In any case, this is probably a question best answered by a Gigabyte engineer.

As a side note, given the age of that motherboard it's not particularly surprising that it may be encountering issues.
 
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Roberto Bustos

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I have a 750 watt power supply. Brand new. It is powering a GA-EP45-UD3P as I type this. :-D All parts I used to power up the UD3R board are working perfectly on the UD3P.

When you say the question is best answered by a Gigabyte Engineer, does that mean they frequent here? Or I should be asking Gigabyte directly?

Robert
 
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Pinhedd

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Hi Robert,

what is the particular make and model of the power supply?

Yes I mean that you should be contacting Gigabyte directly. Many vendors have customer service representatives that frequent these forums but motherboard vendors are conspicuously absent. Given the age of your motherboard it's almost certainly no longer under warranty, but they may be able to help you out.

As a side note, have you tried powering it up after turning off the breaker on the PC (the I/O switch on the PSU itself) and turning it back on after about 10 seconds?
 
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Roberto Bustos

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The PSA is a Sentey 750W Modular PS. I don't have the exact model # handy. 2 weeks old. It is running the computer I am typing from. I have left the computer on for a week now. No issues. Check my signature for what I am running.

Yes I have tried the On/Off switch. This motherboard was sold to me as Not Working. I am trying to fix it. I already sent away for 10 (always need spares :) BIOS chips. Got the programmer ready to go! I can change them easily, but I still don't know if that would solve it or do I need to be looking for another chip on the motherboard. I have 2 others as well. 1 UD3P with socket pin broken off and another UD3R that trys to turn on when power pins are shorted but turns off after a few secs with no post. I *could* use them for parts, but I usually just order them as the other UD3R is on the list next to get fixed :)

Robert
 
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Roberto Bustos

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Oh.. the reason I am fixing the motherboards is I have Xeon X5492's and Dominator memory ready to go on them :-D

They might not be as fast as I7's, but for the price difference and still ultra fast speed, they are well worth keeping around!!

Robert
 
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Pinhedd

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I highly doubt that it's the firmware chip, that's nothing more than a 1 megabyte EEPROM. The memory controller maps the EEPROM into the lower 1 megabyte of the physical address space which is addressable when the microprocessor is reset. In order for this chip to do anything meaningful the machine has to be powered on first.

When you clear the firmware settings via a switch, button, or jumper all it does is disconnect the power to a small SRAM chip (often called CMOS, but this is a misnomer) which stores the firmware settings. The power loss causes the SRAM chip to lose its contents which will force the firmware to fully reinitialize everything the next time the board is powered up.

When the machine is not plugged in, essential motherboard components including the SRAM chip, real time clock (this is how your PC keeps time even when its turned off), and optionally some control circuitry are powered by a small 3.0 volt lithium button battery.

Newer motherboards store the firmware settings in non-volatile Flash memory alongside the firmware code itself (rather than in older EEPROM) so the battery only powers the real time clock in many modern systems.

My suspicion is that there could be a fault somewhere in the control/monitoring hardware rather than in the firmware.
 
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Roberto Bustos

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Yes! I agree with you. I just need to know which chip it is (that "turns it on"). LOL!

The BIOS might have triggered a "safety" feature to prevent further damage and when I clear the CMOS, it forgets and then triggers the "safety" feature again...?

Oh.. I still needed the BIOS chips as the other MB turns on for a few seconds but the CPU doesn't finish initializing (as per the LEDs on it) and then turns off. I'm 90% sure its the BIOS. I have an on-board programming clip, but I would need to bypass the power protection on the programmer (the MB sucks up power as I try to program the BIOS) and since the programmer is under warranty, I am reluctant to do so atm. Maybe in a few months :thumbsup:

Robert
 
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