PC restarting repeatedly, eventually boots.

[Loony BoB]

After shutting down my PC, it has started booting for about 2 seconds, fans and lights, then effectively restarting over and over until eventually it boots. The main thing I note is that when it DOES boot, that's then the LED codes start popping up on the Gigabyte board - before that there's nothing on the code display at all while it's rebooting constantly.

Unplugged drives and graphics card, still happens. Tried new power supply, still happens.

I'm unable to easily remove the RAM due to the cooler being smack over the top of them, but that's going to be my next hopeful fix - after that I know I'm looking at the system board or CPU. Any thoughts on how best to diagnose which one it is? Both are still under warranty (three months shy of three years old) but as they're obviously with different manufacturers, I've no idea which one to go to!

Tempting to just go for a Kabylake 4.2GHz and grab a new mobo but I have to remind myself that the stuff I have is still very good spec and in warranty... but... urgh spending time without a PC would be murder. At the moment the PC is still at least eventually booting, and if I never shut it down it's fine. But yeah. Any advice is welcome!

EDIT: Should probably note that I hadn't changed anything on the PC around the time this started happening, so likely a faulty item rather than a setup issue. But happy to be proved wrong!

 

[Loony BoB]

Not overclocked (I know, I know... I'll figure it out someday... maybe). Will clearing out the CMOS still help with that in mind?

Tried a new outlet + power cable (completely different room), no change.

Gigabyte Z97X-Gaming 7 Intel Z97 (Socket 1150) DDR3 ATX Motherboard
Intel Core i7-4790K 4.00GHz (Devil's Canyon) Socket LGA1150 Processor - Retail
500GB SSD, a few older drives
EVGA 750W psu, Gold 80
Alpenföhn Brocken ECO CPU Cooler - 120 mm
16GB RAM, unsure of spec
Gigabyte GeForce 980
Bunch o' fans and a box.

 

[Loony BoB]

Checked each stick of RAM in DDR4_1, one at a time, no change. Haven't got to CMOS yet but thought I'd post this as it's the first time I've seen it. Most of the time it's just doing the whirring of fans then restarting in a couple of seconds, but then there was this on one occasion...

Apologies for filming vertically

EDIT: Working on CMOS now. The eventual restart just isn't happening for me so will do it on the board.

 

[Loony BoB]

There's thankfully a button for resetting CMOS on this board. Nothing changed, unfortunately. =/

 

[Loony BoB]

Already done that exactly earlier, no dice. =/ Thinking at this point it may just be a rather dead SBD/CPU

 

[Loony BoB]

Yeah, used a new PSU (Had to buy one for the girlfriend's rig anyway) and it didn't make a difference. I did remove all the memory and tested them one by one with no difference.

Read up a few other threads on various forums and in two of the cases it was a RIP CPU. Looking like that might be the same for me. I'll make attempts to clean up and redo the CPU and cooler once I find my alcohol but outside of that, I fear I'm out of options.

So... how are those Kabylake 1151? :')

 

[Loony BoB]

Excuse me for being an idiot: What is it that would cause a BIOS to get borked? Isn't it safe from the start to finish, provided you don't change hardware?

 

[Loony BoB]

Just read over your thread. Bizarre! What did you end up doing? Buy a new CPU or board, or...?