ASRock X99 Extreme4 boots only on cold boot

[N3Star]

Hello,

The motherboard in question boots only on cold boot - if I cut power to the PSU it will boot fine, but as soon as I reboot from Windows or even short reset pins it goes into bootloop - 1 second on, a few off and so on.

Initially the board arrived to me broken - bad PCH, after replacing it it worked for a while. I suspected a bad connection, but pushing the IC down does nothing. I don't really think that the PCH is dead, since it still boots and works fine until I reboot the PC. Obviously I tried looking for something that heats up or bad caps, but nothing so far.

I tested the CPU, PSU and RAM in other boards, they work absolutely fine.

Any ideas what else I can test?

[wisjg]

Check if the resistor under the network card chip has been knocked off. If so, it might have been accidentally knocked off during graphics card installation. Reinstalling it should fix the problem.

[N3Star]

Thanks for the suggestion, I'm unable to see any missing components around the network controller, same on the bottom side of the PCB, but take a look at it youself, maybe I missed something.

[wisjg]

I encountered an ASUS motherboard before with a similar problem. It turned out the SMB bus resistor between the SC and LAN ports had tripped. You can check that area. Hopefully, this helps.

[N3Star]

Well, I guess I found the problem - I tried searchig for missing resistors, but all of them measured correctly, however when I tried to power on the mobo I got no power. I checked the pwrbtn# line and it goes low, so I guess the replacement PCH has failed. I'll try and edit this post when I replace the PCH again and it works/doesn't work again.
Thanks for the help so far