Calling all coroners: Cause of death, mobo, or CPU?

As mentioned elsewhere, my Threadripper 2950wx-equipped Asrock Fatal1ty X399 gave up its ghost. A few RGB lights still on, but no reaction to power-on, no DrDebug countdown. I now need to determine whether it’s the mobo, or the CPU. Sorry, don’t have any friends who would let me swap-in my CPU … Any pointers on how to determine whether the CPU or the mobo is the cause of death? With my luck, I’ll buy a new mobo, and then it was the CPU (or v.v.) Thank you!

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i have come across many bad motherboards personally and on the job, but never a bad cpu. in one of the old vids wendell mentioned seeing two bad cpus in his entire career. it’s almost always the motherboard not the cpu.

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Mobos usually have ability to at least display initial (probably 00) code even if CPU is not present (that kind of suggests that from two possibilities CPU/MB its probably MB).

You can check your MB’s manual, if apart from the code display the MB also have LEDs near major components indicating what of the main components is being initialized (CPU, RAM, GPU).

If you have dual BIOS you can try switch to the other (sometimess MB are designed to do this automatically).

Additionally, if you have not tried it earlier:

  • Clear CMOS ( you might loose BIOS RAID if you have setup one).
  • Try to install BIOS from flash drive (some mobos allow for update without CPU - it might actually require removal of CPU).
  • I know, I might be to optimistic (based on the symptoms), but at least I would do it.
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Thanks, all tried, no joy. BIOS display is totally dark.

As far as the bad CPUs go, I had a few fried ones in the olden days :slight_smile:

there is an old school dead cpu test…
you turn the pc off at the back… turn on your monitor and time the time it takes for the screen to go from showing no signal, into standby… 3-10+ seconds depending on the screen.
now turn the screen off and on again. this time when you see no signal hit the power on the back of the pc (dont turn on the front power yet)
id the screen stop showing no signal? did it imediatly jump into stanby? quicker than before when the pc was off?
last test…
turn the screen and pc off again…
turn the screen on, wait for no signal then hit power on back if its still no signal hit power on the front of the case…
again did it go into stanby straight away?

if you hit power on the back and the screen showed no signal and didnt jump into standby then it means residual power isnt getting to the gpu. and the motherboard is at fault… you should also notice the fans spin up and shut off.

if it the monitor immediately jumped into standby as soon as you hit power on the back or front. then the cpu is normally the culprit. as the board has powered up but the cpu has told the gpu to sleep the system because theres an error.

this is an old school test from back in the p4 days… it worked with both amd and intel. and i tried it 3 weeks ago on an intel build it still worked as a diagnostic test… so try it with the thread ripper. it may still be a diag tool for that 2.

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Thanks, I’m VEEERY old school, back from when CPUs had 8 bits … That mother is totally dead, no screen at all. BTW, I noticed that one of the 2 fans of the Noctua NH-U14S TR4-SP3 cooler had gone dead also. Maybe it fried the machine. Based on the advice received, I just ordered a new mobo, a X399 Designare. It was on sale. Fingers crossed that was it …

Ive replaced a few cpu that were dead (primarily because the clients cpu cooler fims were so clogged with dust they were entered in the dust bunny hall of fame)
generally a board wil also beep a code for parts failures. but if no beep or no display its a good bet its either power supply or cpu, fans run, cpu

Not always a sure bet, motherboard speakers are increasingly rare.

Update: It was the motherboard. Replaced, works.

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I’d say it normally is in my experience, and if it IS the CPU, I’d be blaming the motherboard for killing it (unless there’s an explanation from some other user-incurred abuse via voltage, etc.).

Additionally boards are normally cheaper than CPUs, so starting with the board Is usually the best bet IMHO.

Unless it blew up in a lightning storm, your cpu will be the last thing in your system to die. 20 years from now my 3900X will still be kicking away.

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