[SOLVED] Aorus X570 Ultra showing CPU temperature -55C and sometimes no boot.

[rag0n]

Hello.
Some days ago after a boot i noticed that my pump fin was not spining at all after the post. It spinned for a few seconds befor post but then it stopped. I got in the bios settings and I noticed that the cpu temperature was read at -55C. I got in smartfan 5 and i got it to work only by setting the fan mode to PWM instead of automatic. I also set it to full speed. I have my pump connected to cpu_opt port. HWinfo64 and Ryzen master can succesfully show me the cpu temps. Other problems i faces are the foolowing.

1. Sometimes my pc doesn't post and it is stuck in cpu check led untill I completely kill the power from the psu for a few seconds and then i get it back on. Then it posts ok.
2. 2 times when i booted into windows and tried to launch ryzen master i got a failed to initialize error kindly reinstall and after the second reinstall im now unable to get it to work.

My rig
ryzen 3800x
Aorus x570 ultra
trident Z rgb 2x8gb cas 16 3600 mghz samsung die
rm750x by corsair
cougar helor 240 AIO cooler
rog strix gtx 1080
Any suggestions would be really helpful
screenshot of my mobo cpu temp
http://rag0n.tplinkdns.com/index.php/s/fPRHCenS5rtaNDb

 

[rag0n]

So, I solved it and I'm going to leave this here to help anyone else with the same problem. It was a real nightmare.
I noticed that even with the computer disconected from the wall power my CPU LED in the post code was not going completely off and i thought it had something to do with the problem. I started unplugging peripherals from the pc. When i unplugged the displayport from my gpu i noticed it went off. Note that the displayport was my 2nd monitor connection as i have my main monitor plugged by dvi.
Now everything is normal. Temperature readings inthe bios are back and boot is fast and proper.
As this video states

View: https://www.youtube.com/watch?v=6s1cMwzesZI
some displayport cables have a pin on on position 20 which can deliver power to your pc that they shouldn't have causing those problems. I hope this post helps other people too and buy branded DP cables.

 

[GarrettL]

Thanks for documenting the solution. Well done!