PC Repeatedly rebooting to BIOS screen but works after PSU off/on and boot

MattG50

Commendable
Dec 15, 2016
2
0
1,510
Hi, hopefully someone has the expertise to solve this really puzzling problem.
Symptom: PC reboots itself to BIOS title screen and then powers off, reboots itself and repeats. Sometimes the duration after the reboot is 1 second, sometimes its 5 seconds (and inbetween). However if I power OFF the power supply at the mains / or the switch on the PSU and THEN reboot using the front switch it ALWAYS boots correctly. Once it boots into Windows10 or MacOSX (Hackintosh) it is 100% rock solid even when Geekbench stress tests or Intel CPU stress tests with temperatures never going above 45 degrees C.

Case: Fractal Design R4 (new)
Motherboard: Gigabyte H97n-WIFI
PSU : EVGA 750W Supernova Modular
CPU: Intel i7 4970S
Memory : 2 x 8Gb sticks
Boot Disk: 1Tb SSD using Clover
Cooling: Corsair H100i V2 using USB on internal header

More detail:
I had a 100% working system with all of the above components except the case (new) and PSU (new). I was using the system and then the PSU failed quite dramatically, so I purchased this new EVGA PSU and plugged it in with the expectation that it would fail dramatically either the motherboard or CPU were possibly fried - but no, it booted fine.
In rebuilding the PC I decided the old Mini-ITX case was too tight so I purchased the Fractal Design R4. Currently its power switch is only plugged into the Power front header, no reset plugged in.
Basically when I boot from cold (previous full power off), it boots to Clover 100% of the time and then to either Windows 10 or Mac OSX 10.2 Sierra perfectly. Then select shutdown from either OS, the machine powers off correctly. Then I press the power button and it going into BIOS - but not full BIOS, just the Gigabyte header at the top and then reboots again, and again and again. If I then switch off the PSU and restart, it works 100% of the time.
So it cannot be overheating or a loose connector as it would crash once it boots into an OS. I can play for hours in a heavy game and its a silent system, no crashes ever. So why would a reboot after shutdown be especially problematic?
I've tried various BIOS settings for power and fans, but can't see any change in the previous bvehaviour. I'm inclined to think its linked to the Fractal Case but can't be sure. Any ideas?
 
Solution
sounds to me like a broken motherboard bios causing a boot loop. you could try updating/flashing the motherboard bios to see if that resolves the issue. bios flashing needs to be done correctly so follow the instructions carefully if you decide to try.
sounds to me like a broken motherboard bios causing a boot loop. you could try updating/flashing the motherboard bios to see if that resolves the issue. bios flashing needs to be done correctly so follow the instructions carefully if you decide to try.
 
Solution

MattG50

Commendable
Dec 15, 2016
2
0
1,510


Thanks for the suggestion, I did reflash downgrade the BIOS with the Gigabyte v8 and then updated to v9b plus reset it with the BIOS jumper setting. However this didn't solve the behaviour, it seemed to reoccur when pressing the power button but when performing a 'restart' in software, the behaviour was different.
I found the solution, but slightly by accident. In the rebuild since the power supply was changed and new case installed, the SATA ports must have been plugged into different connectors on motherboard. As I'm using Clover as the EFI boot loader, it seemed to be getting confused with where to boot from. I kept changing the boot partition but bizarrely it would change after a power button press. I still can't work that one out.
I pulled one of the EFI SSD boot disks (for repurposing) I had previously used and all of a sudden the box boots from the correct boot partition and 'remembers' the right primary boot disk/partition for Clover. Now it doesn't 'hunt' for a boot device and restart itself during the boot process. All stable.
Thanks for the help, I think it contributed to the overall solution.