[SOLVED] CPU boots only in one of three "sane" motherboards

Jul 31, 2020
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My build suddenly stopped working, and a friend of mine lent me two motherboards he had to test.

The components in question are
  • CPU: FX 6300
  • PSU: EVGA 600B
  • Motherboards:
- The one I was using: Asus M5A78L-M LX3 (let's call it A),
- One from my friend: Asus M5A78L-M LX V2 (B)
- Another one from him: Asus M5A87 R2.0 (C)

Mother A was my system's board and my FX6300 was getting very high temperatures on it. About 40 degrees celsius idle and up to 95 degrees on load (maximum critical temperature reported for this processor). Eventually, it would shut itself off or completely freeze. Sometimes it didn't start on the first attempts but after two or three. About a month ago it completely stopped working, booting made the CPU and PSU fans go on, but no video output nor motherboard speaker beeps (not even without the ram sticks).

I did the usual: remove MB from chassis, boot only with CPU, RAM and PSU. I checked the memory sticks with another machine. The PSUs were not checked though.

Fortunately, this friend of mine had two MBs with AM3+ sockets for the FX6300 to lent me, mothers B and C.

Mother B, which is the same small form factor, and my friend was pretty sure worked*, did not work. The result was a bit different though, with my EVGA PSU, fans started but quickly stopped. With the generic PSU, it worked the same as with MB A.

(*The story of this MB is that my friend bent a pin of the processor and when corrected, the system did not boot anymore, so he thought the CPU was the one who died.)

MB C on the other hand required to connect my GPU (GTX 960) as it does not have integrated graphics. I think I had to tinker a bit because it did not work at first, but I might be wrong, the thing is it worked eventually, I got an image on the monitor, then bios, then OS booting. Yay!

Not only it worked, but also all my old temperature problems were gone, like 5-10 celsius idle and up to 60 celsius on full load (CPU and GPU 100%).

My question is, assuming board B works, could it be that somehow a bigger/better motherboard solved the problem for a broken CPU, if so why? or maybe mother B broke (right after the bent pin accident), both motherboards A and B are failed, and the CPU still works properly? Which scenario do you think is more likely?

I would love to hear what are your thoughts on the situation. In any case, thank you for the useful forums (first post here :))!
 
Solution
Sounds like boards A & B failed if C is working 100% with zero issues

board A could have a bad regulator feeding the CPU making it overheat (too much voltage)

Board B a pin inside the socket could of bent or broken or something is in it making it not function correctly. or it could be a bad part that makes the trigger for the psu to make it stay on that is not working properly which is why it powers up and off imediatly.

thats my guesses.
Jul 30, 2020
17
3
15
Sounds like boards A & B failed if C is working 100% with zero issues

board A could have a bad regulator feeding the CPU making it overheat (too much voltage)

Board B a pin inside the socket could of bent or broken or something is in it making it not function correctly. or it could be a bad part that makes the trigger for the psu to make it stay on that is not working properly which is why it powers up and off imediatly.

thats my guesses.
 
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Solution
Jul 31, 2020
3
0
10
Didn't know about the existence of the voltage regulator, thanks for that one.
I hope that's the case, my main concern is buying a cheap AM3+ motherboard and it not being able to boot because the processor was being the faulty component.
 
Jul 30, 2020
17
3
15
Didn't know about the existence of the voltage regulator, thanks for that one.
I hope that's the case, my main concern is buying a cheap AM3+ motherboard and it not being able to boot because the processor was being the faulty component.

Thats what the 4 or 8 pin connector for the cpu plugs into. It sends it to regulators to step down the 12V down to the voltage that the cpu can use.
 
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