Existing Build Won't POST or Boot GA-Z270

Apr 2, 2018
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I'm unable to get my 14 month PC to boot anymore. When I reset the CMOS via jumper pin and reboot with no RAM I get 5 long beeps. When I reset the CMOS pin and reboot with RAM, I just get a constant power up, fans spin and then power off loop with no beeps.

History:
1. After a Windows restart my PC was in the BIOS screen;
2. I tried rebooting from here and it said that SecureBoot had been disabled and wanted my BitLocker key
3. I rebooted and found a setting for SecureBoot in the bios (I did not write down exactly what this was).
4. After enabling this setting and rebooting the PC has gone into a constant spiral of power on, fans spin up and then power down with no beeps.

I have since followed the guide as best I can - I do not have easy access to spare PSU or RAM. I have reseated all power cables and removed all hard drives/video cards.

As per the intro, the only way I can get different behaviour is by removing the RAM, resetting the CMOS and then powering on. Here it will spin up and down in silence as per normal, then reboot and produce 5 long beeps, then reboot and spin up and down in silence and then reboot with the 5 long beeps - repeated in a loop.

I've also moved the RAM in and out of both positions DDR4_1/DDR4_2 and DD4_3/DDR4_4 - noting that it was in DDR4_1 and DDR4_2 when previously working.

This build has been relatively stable for 14 months although I did have some strange boot issues when I was first putting it together which I can't remember the specifics of.

Specs:

  • Intel i5 7600
    Gigabyte GA-Z270-K3
    Corsair Vengeance LPX 16Gb 2x8Gb DDR4 3200MHz
    Corsair CMPSU-620HX (approximately 10 years old, carry through from a previous build)
    Thermaltake Soprano DX (carry through from a previous build)
    Windows 10

    Gigabyte TPM 1.2 Module (Disconnected)
    Samsung Evo 960 250Gb M.2 (Disconnected)
    Couple of spinning drives (Disconnected)
    XFX Video Card (Disconnected)
    All USB devices disconnected including keyboard/mouse at this time

Link to video if anyone wants to see - this is with RAM removed and the cycle with the 5 long beeps.

Any further ideas appreciated

thank you
 
Apr 2, 2018
2
0
10
I couldn't spend any more time troubleshooting so I went and bought another motherboard (Gigabyte Z270-HD3). This posts and does not have any issues with the exact same other hardware (CPU/RAM/PSU etc).

I've since found a few other threads:
https://forum.giga-byte.co.uk/index.php?topic=18475.0
http://www.tomshardware.com/answers/id-3373394/gigabyte-z270x-ud5-boot-loop-caused-secure-boot-setting.html
https://forums.tweaktown.com/gigabyte/55004-secure-boot-enabled-system-wont-post.html

It looks like enabling Secure Boot in the BIOS causes this issue. The only way to fix this appears to be to short the CMOS out - which I did briefly try with no luck and couldn't risk it not working so went and got a new motherboard. Pretty disappointing!