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NZT48

PC won't boot after clearing CMOS while turned on

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System specifications: Intel i7 3770K / i5 3570K CPU, ASUS Z77 Sabertooth / MSI GD65 Z77 thing motherboard, 2 x 8GiB DDR3 RAM, ASUS GeForce GTX 1070 OC thing, Corsair AX860 PSU

Problem: PC turns on briefly, lights light up, fans spin up. After a few seconds it turns off then after a couple of seconds it turns back on, etc. There is no display.

Probable cause of problem: The CMOS was cleared while the computer was turned on.

What I have tried: I tried a different and much more powerful PSU, I tried taking the video card out and using the on-board video, I tried taking the RAM out, I tried another motherboard, I tried another CPU.

Any help would be greatly appreciated.

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Is it possible I originally killed the CPU and then when I tried the CPU in the replacement motherboard the CPU killed that motherboard?

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The common advice is that setting the clear CMOS jumper or hitting the button while the thing is powered on is bad, though they don't say why.

IMO could be that it's damaged the SMC or some other component/s but I doubt the graphics card, RAM or CPU has suffered, more like a motherboard component.
You could examine the board for shit-stains.  I'd try powering up without the coin battery and ensure the clear settings jumper is set to "normal" (that's another thing, in some cases having no jumper can cause problems).

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I've tried replacing the motherboard though.

What does "SMC" stand for?

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SMC  - System Management Controller.  Or equivalent.  Generally they sit there on standby current or using microamps on a laptop - they do stuff like power the system on, resume from sleep by lid opening etc.

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I've never cleared the CMOS while the PC is running, I don't want to find out either. I guess I know what to expect now ...

 

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I think I've got a P4 board that could be a sacrificial testbed but I suspect the result wouldn't be an indicator of what to expect with every board.

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On 9/15/2018 at 9:01 PM, NZT48 said:

: PC turns on briefly, lights light up, fans spin up. After a few seconds it turns off then after a couple of seconds it turns back on, etc. There is no display.

How many cycles have you let it go through? With modern UEFI systems a bios change or bios reset can make the system do a boot/reboot multiple times as it updates system parameters. However if it's doing the reboot past 4 or 5 cycles something is probably screwed or set wrong.

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22 hours ago, aliali said:

How many cycles have you let it go through? With modern UEFI systems a bios change or bios reset can make the system do a boot/reboot multiple times as it updates system parameters. However if it's doing the reboot past 4 or 5 cycles something is probably screwed or set wrong.

I reckon it has gone through at least 7 cycles.

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