ROG STRIX Z270-I Gaming running very (very!) slow

[RP22]

I'm helping a friend with their misbehaving computer.

Motherboard: ROG STRIX Z270-I Gaming
16 GB RAM
System drive: Samsung 850 EVO 1TB SSD

Whoever built the system for her used a rather large case for such a small mobo and used a Cooler Master liquid cooler with a 120mm rad and fan. The radiator was very blocked with dust as were all the case filters. All this might have caused some overheating.

The problem is that the system is taking over 5 minutes to boot and when Windows 10 finally loads everything run very slowly.

Here's the current startup timing (m:ss):

0:00 - 0:20 : computer starts, a yellow light lights on motherboard for 10 seconds and then goes off.

For the next 4 minutes nothing happens even though the computer is running

4:34 - 5:12 : a white light lights on motherboard

5:12 : the computer turns itself off and restarts

5:16 : same yellow light lights on motherboard for 3-4 seconds
Monitor powers on
ASUS logo and "Press F1 for setup" options text appears briefly (3-4 seconds)
Windows10 loads and starts, but performance is very poor.

Shutting down the computer closes Windows and turns off the monitor quick quickly, but the computer itself takes 5 minutes before powering down.

I updated the BIOS to v1205, cleaned everything up, removed the discrete GPU and am running the monitor off the builtin HDMI port. I installed a new battery in case it was weak and causing some issue with the BIOS.

Tomorrow I'll try a new power supply. But it's been my experience that a system just won't boot with a bad PSU. I'm starting to suspect the motherboard has a problem.

Does this sound like a broken motherboard or might it be something easier to fix?

R

[RP22]

This morning I rebooted the system and after 20 minutes with not proceeding past the white light I gave up,  shut down, pulled the power plug and pressed the power button to clear all the capacitors. 

It then restarted with the yellow light for a few seconds, a white light at 8 minutes and the green light lit at around 10 minutes. I loaded the BIOS setup and found it extremely sluggish. Anything I did (like press F7 to toggle EZ/Advanced) was taking 15-20 seconds to execute. My mouse cursor never appeared. All the temperatures seemed reasonable (mobo 23ºC, processor 31ºC). I noted that the CPU voltage is .992V

I decided to just restart and pressed the power button. The computer restarted immediately with a green light and the splash screen. I  loaded the  settings setup menu and saw that the CPU voltage is 1.008 V.

Windows loaded as quickly as one would expect and seems to be performing properly (for now...).

Anyone have any ideas of what the culprit likely is ??  (CPU, Motherboard, PSU)

R

[RP22]

So ... when the system boots and stalls at any one of the four LED code lights I find that holding the power button until the system restarts will again pass through the 4 lights: Red (CPU), Yellow (DRAM), (VGA) White and  Green (boot_Device). On 1 out of 3-4 attempts it WILL pass quickly through all four  ( = normal boot behaviour) and the system boots quickly and Windows loads . I must always repeat the OFF/ON routine a few times until I achieve a clean pass through the 4 LED light stages.

That's where it is now.

[RP22]

Just swapped the RAM with two DDR-4 sticks (on the QVL list) that I had in an another working system and it's not made any improvement. Same behaviour as before.

[RP22]

Had a spare high quality PSU that I just connected to the system and it's not made any improvement. Same behaviour as before.  Looks like all that's left are the CPU and motherboard which I don't have any spare to test with.

R