Wednesday 6 February 2019

boot - Troubleshooting PC power-on irregularity, narrowed down to ASUS VRM Spread Spectrum, why?


There are many resources online regarding the issue when the PC shutsdown a few seconds after pressing the power button. I have a variation of the problem which is reproducible under certain conditions. I would like to hear the community's thoughts on what may be causing it. Found a solution, scroll to end of post, I would still like some more information to rule out a problem with my motherboard.


Scenario


When the computer is powered off for a fair period of time and then powered on maually:



  • Computer powers on fans spin for ~3 seconds (No POST beep)

  • Computer shuts down

  • Computer powers itself on immediately afterwards

  • Computer abpruptly shutsdown (<1 second after it turns itself on) - computer remains off


After the above, pressing the power on manually resumes normal startup, POST beeps once. Computer operates as normal.


Other power on/off combos tried that do not show the above issue:



  • Restarting the PC using either the software reset or manual works fine, Computer boots normally

  • Shutting down the PC either by software/hardware and then immediately powering on works fine.


Things I've tried:



  1. Clearing the CMOS - did not help

  2. RAM is fine (tried bench testing with one module at a time)


Unfortunately I do not have another PSU to test with. Here are my system components:



  1. ASUS VI GENE MB

  2. INTEL i7-4770k CPU

  3. 32GB GSKILL 2133MHz running at 1.5V

  4. SEASONIC Platinum Series 520W PSU 520FL

  5. ASUS GeForce 670GTX


All components are less than a year old so luckily under warrantee.


Guidance appreciated.


EDIT: whenever the issue occurs I'm prompted to enter BIOS by pressing F1 as the overclocking presets are lost. but entering BIOS shows my config as it should be and I exit without making any changes and the PC starts normally.


EDIT: CPUID HWMonitor Output


CPUID Output


EDIT & SOLUTION: I played around with a fresh start on BIOS and slowly enabling one by one the options I had set. Doing this I enabled the ASUS motherboards VRM Spread Spectrum, its description saying it improves system stability... WRONG!! this is the thing that caused my power on problems. I suspect on some occasions the motherboard fails to provide the CPU the voltage it requires and fails the POST. Also I did some reading here -> http://www.overclock.net/t/1401976/the-gigabyte-z87-haswell-overclocking-oc-guide and they say the Haswell processor has inbuilt VRM's so it is not needed to be done by the motherboard. Having ASUS VRM SS disabled in BIOS fixes my power on problems.


I'd like to ask the community to rule out motherboard issue, Does anyone run an Haswell setup i7-4770k with VRM SS enabled in BIOS and it is working for them?



Answer



Problem is BIOS's VRM Spread Spectrum causing boot instabilities, disabling this on the ASUS motherboard fixes the problem and the PC POSTs every time.


Waiting on more information from ASUS as to why it says that the option is recommended and it will improve system stability in BIOS.


I enabled it because it is said to reduce EM emissions as the PC I work on is part of my radio lab.


Here is some info on Spread Spectrum and why you would use it -> http://www.ni.com/white-paper/4154/en/


Why it should be disabled if you are OC'ing -> http://www.techarp.com/showFreeBOG.aspx?lang=0&bogno=266


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