Question Pc only starts after CMOS clearing!!!

rodrigogamba

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Aug 14, 2018
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Hi everyone,
The thing is my PC was running normally at night, but the next morning when I turned it on, it began with a boot loop. The CPU cooler fan and the GPU fans started to spin for just 2 seconds, then the PC turned off and tried to start again, doing the same, getting in a boot loop until I unplugged the power cord. I tried to remove the entire hardware leaving just the PSU , and CPU, and I had the same trouble. I never get a beep because the PC never gets the POST stage.

Then I did a CMOS clearing removing the CMOS bottom cell, and magically the PC booted. I had to reconfigure MOBO time and date, and after a restart I finally could get on Windows, and the PC worked perfectly fine until I turned off. The same boot loop again!!!!! I did a CMOS clearing again but this time putting the CMOS JUMPER in pins 2 and 3 for a few seconds and putting back again in pins 1 and 2 with the PC turned of and unplugged. And it worked again!!!.

So I realized that Everytime I clear CMOS, removing de bottom cell or with the CMOS JUMPER , the PC boots normally. It goes through the POST stage, a little bit longer than normal, but finally it sounds the single beep that indicates that everything is good. First I get to the bios to reconfigure date and time, save changes and the then, After a restart, I can get into Windows.

I already tried changing the CMOS bottom cell for a new one, and still having the same problem.

Now, if I'd like to turned off my PC, I have to do a CMOS clearing every time I turned it on again.

I will be very grateful if you could help me with this.

My hardware
CPU: I7 4770k
COOLER: 212 EVO
GPU: Gtx 1080
RAM: 2 x 8 GB DDR3
PSU: Evga 750 +80 BRONZE
 

vov4ik_il

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Mar 23, 2020
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Can you try this:
  1. Install a new battery (you mentioned that you do have one)
  2. Make the computer boot normally. (use your trick with CMOS clearing and bios setting).
  3. Shut it down normally
  4. Unplug the power cord for 45 sec and plug it back in
  5. Try powering on and see if it boots
 

rodrigogamba

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Can you try this:
  1. Install a new battery (you mentioned that you do have one)
  2. Make the computer boot normally. (use your trick with CMOS clearing and bios setting).
  3. Shut it down normally
  4. Unplug the power cord for 45 sec and plug it back in
  5. Try powering on and see if it boots
I tried step by step you mencioned. No fix yet. still need Clear the CMOS to make it boot
 

vov4ik_il

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There are a few options in BIOS that you can try to disable:
  1. Boot: Fast (Ultrafast etc) Boot
  2. Power Management - S1-4 states
Edit: Also when you set-up bios after clearing, do you enable CSM?
 

rodrigogamba

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There are a few options in BIOS that you can try to disable:
  1. Boot: Fast (Ultrafast etc) Boot
  2. Power Management - S1-4 states
Edit: Also when you set-up bios after clearing, do you enable CSM?
the CSM is enabled by default. Already tried disabling fastboot, and cpu power managmnet states.

It seems the mobo saves the default settings just once, after clearing, but once it starts, saves another configuration that dont let the pc boot normally.

I read in other threads that my be the mobo or PSU are fried, but I'd think if it's capable to boot and work perfectly fine once in windows without crashes or BSOD or anything else, it might not be a hardware problem.

what do you think?
 

vov4ik_il

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what do you think?
I am not sure. If there would be a way to verify that the CMOS settings get corrupted (dump them with a reader and a clip and compare after shutdown), I would send the board to the vendor or (if no warranty left) replace the CMOS IC myself (probably 3$). But that's me.
Edit: unless you are comfortable with the component level repair (BGA), try to change a few settings and then reboot and see if those setting stay after POST.
 
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rodrigogamba

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I am not sure. If there would be a way to verify that the CMOS settings get corrupted (dump them with a reader and a clip and compare after shutdown), I would send the board to the vendor or (if no warranty left) replace the CMOS IC myself (probably 3$). But that's me.
Edit: unless you are comfortable with the component level repair (BGA), try to change a few settings and then reboot and see if those setting stay after POST.
OK, this is quite a bit advanced for me. hahahaha, but i can try.

"(dump them with a reader and a clip and compare after shutdown)"
i didn't understand the way to verify if the CMOS settings get corrupted.



"replace the CMOS IC"

You mean replace the complete bios chip? like this one?
http://www.bios-chip24.com/Asus-Z97-A/USB-31/es

rebooting the system do not have any issue. every change I made in BIOS settings stays in place, and the pc boots normally. The problem appears when the pc gets out of power. (Both, wheni turn it off and sleep)

edit: I forgot to explaine it before, but it also happens when I sleep or suspend the PC.
 
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vov4ik_il

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OK, this is quite a bit advanced for me. hahahaha, but i can try.
For the board you have, it is not worth the hassle, just if you want to tinker with stuff :-D

"(dump them with a reader and a clip and compare after shutdown)"
i didn't understand the way to verify if the CMOS settings get corrupted.

"replace the CMOS IC"

You mean replace the complete bios chip? like this one?
http://www.bios-chip24.com/Asus-Z97-A/USB-31/es
The IC you show is a FLASH memory which stores the BIOS, while the CMOS data is usually stored in the memory on the SMC itself, and stays there as long as there is a power to the IC.
It is this kind of job. I regret to mention it as it does not look like you gonna like it 8-D

rebooting the system do not have any issue. every change I made in BIOS settings stays in place, and the pc boots normally. The problem appears when the pc gets out of power. (Both, wheni turn it off and sleep)

edit: I miss explaine it before, but it also happens when I sleep or suspend the PC.
That strongly suggests that the IC does not get proper power from the battery or has its memory corrupt once PSU stops/starts delivering power.
 
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rodrigogamba

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For the board you have, it is not worth the hassle, just if you want to tinker with stuff :-D


The IC you show is a FLASH memory which stores the BIOS, while the CMOS data is usually stored in the memory on the SMC itself, and stays there as long as there is a power to the IC.
It is this kind of job. I regret to mention it as it does not look like you gonna like it 8-D


That strongly suggests that the IC does not get proper power from the battery or has its memory corrupt once PSU stops/starts delivering power.
Ok, I understand, I think... XD
So what do you suggest I should do?. I'm just an average Computer user, whith an average Knowloege about systems. i've never done the SMC replacement and i don't have any idea how to do it.

May be if there is an easy and harmless way to check if the IC data is corrupted.
 

rodrigogamba

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When I think about it, it might be your PSU is not delivering standby power, you will need a multimeter to check it.
You can use this post.
I think i can do that. Tomorrow i will find a multimeter, and I can also try with another PSU.
So, should i measure the voltage in every PIN of each conector? I mean in power conector, cpu conector, gpu, etc?
Do The PSU must be pluged to the wall and turned on?

EDIT: Is it necessary to concect a ground pin with the Power pin?
sorry for all the questions, I'm a bit new in this world.
 
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vov4ik_il

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I think i can do that. Tomorrow i will find a multimeter, and I can also try with another PSU.
So, should i measure the voltage in every PIN of each conector? I mean in power conector, cpu conector, gpu, etc?
Do The PSU must be pluged to the wall and turned on?
For standby power, just disconnect the wide connector from the motherboard and measure between the "+5V Standby"(maybe purple, check location against the linked picture) and any of the grounds (usually black).
Yes, it has to be plugged in when you do it. Skip to swapping if you are not comfortable.
And check the battery voltage too if you are going to have a chance.
 

rodrigogamba

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Today I bought a multimeter and I measured the battery voltage and the purple +5V standby PIN.
Everything looks normal o_O
I couldn't get the PSU today, may be tomorow I culd get another pc to swap between diferent components and give it the last chance.

Do you think it could be a malware or somthing like that?
 

rodrigogamba

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I do not think so, you did try updating bios right? You can do it again to make sure.
You can also do the RAM testing as we mentioned earlier.
Unfortunately both without results. I reflashed the same BIOS version because I already had the most recent. But I'm gonna try it again, to make sure.

And the ram testing too, I did it actually with 4 different sticks.
 

rodrigogamba

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Well, in that case try another power supply but it looks like it is a motherboard issue.
I tried with another PSU and it was the same. Y put my PSU in other pc and worked normally. As you said, it looks like a motherboard issue, may be something with the CMOS settings. Could it be a little short circuit somewhere in the mtherboard? Do you think it is a hardware problem, or the BIOS software?
 

rodrigogamba

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I lean towards hardware. Hard to tell.
I'm still trying to fix the problem, but no good result yet. I was doing some reserch, and the problem seems to be the CMOS memory. Is it possible that wrong information or corrupted data get saved any time I turn on the pc? Because every time I clear de CMOS memory the PC boots.

I tried to find the CMOS memory IC, but I really don't Know where is it. Could you help me to locate it? Coud be something like this?
https://es.aliexpress.com/item/32756151599.html
 

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