New PSU makes CPU to overheat (Help)

[yonef]

Ok, this is the case, I had cheap PSU 600W and decided to go for a quality one. Firs I bought OCZ stealth xstreame. I was damn noisy and my CPU runs 10C hotter than before, I thought it is not relevant to the PSU. I RMAed OCZ PSU, didn't pay attention to high temps because when I revert back to old PSU everything runs cool. Then I bought another PSU ( Hiper type M 780W) very good reviews and good quality. Extremely stable rails, super silent. the problem is that the CPU runs hotter again. WTF ?! How could PSU make CPU to rise temps?

 

[sanchz]

It could, if case airflow depended too much on its fan. Does it have a similar fan to the first one?

 

[yonef]

yep, botto fan 135mm (this PSU) OCZ one has 120mm bottom fan, and my crapy(precious) has 120mm bottom fan. Pretty much the same.
I have one cooler just behind the cpu cooler that pushes hot air from CPU cooler outside the case. Everythig seems the same.
..can the PSU overvolt the CPU but BIOS still says 1.35v ? (silly question) BUT all voltages seem good.
+12V ~ 12.22 12.10
+5V ~ 5.09 4.99
+3.3V ~ 3.37 3.31
Iddle Full load(GPU + CPU)


CPU voltage is 1.352 - 1.355 ( it was like this with all PSUs)

 

[ainarssems]

First thing that came to my mind was that You knocked on CPU heatsink when installing new PSU and loosened HSF contact with CPU but since temps went back to normal with old PSU in place then this is not the case. Is ambient temperatures the same? It could be coincidence that room temps was lower with old PSU.
At last it could down to PSU. If Your old PSU had fan with constant speed fixed at high rpm it was creating better airflow. Or even if it was variable speed it is very likely that cheap PSU was lower efficiency an creating more heat therefor causing PSU fan to work at higher speed and create better airflow in the case.
And very last old PSU could be giving more than 12V on 12V line( very possible for cheap PSU as they overvolt so that at increased load with voltage drop they would not be undervolted ) and gave higher voltage to fans causing them rotate faster and cool better

 

[Nik_I]

At last it could down to PSU. If Your old PSU had fan with constant speed fixed at high rpm it was creating better airflow. Or even if it was variable speed it is very likely that cheap PSU was lower efficiency an creating more heat therefor causing PSU fan to work at higher speed and create better airflow in the case.r

that sounds like a likely answer to the situation.

 

[yonef]

@ainarssems
Old PSU is not fixed fan speed, but it is overheating at load and the fan speed jups to Highest possible. This may create better air flow, but I thought that the heat generated from the PSU(extremely hot, even smells bad) could be worst for the CPU which is 10mm away from the heatsink. Thats why I bought new PSU but instead I got even worse problem.
Old PSU is actualy undervolting my components. Is this can cause them to run cooler?
Old PSU voltages:
idle: ||||| Load
+3.3V ~ 3.3 ||||| ~ 3.1V
+5V ~ 4.9 ||||| ~ 4.4V
+12V ~ 12.05 ||||| ~ 11.4V

Room temps seems to be the same because I did this tests within couple of hours

 

[jsc]

If a PSU is running extremely hot and smells bad, you have a serious problem.

If the 5 volt output drops from 4.9 to 4.4 volts, you have two serious problems.
First, in modern PC, the 5 volt rail is only lightly loaded, probably no more than 6 to 8 amps and certainly less than 10 amp. So you have a bad voltage regulation problem. Second, the 5 volt output drops well below tolerance (4.75 - 5.25 volts).
Third (OK - three problems plus the bad smell), in a well designed PSU, the built in protection circuits would be electronically shutting down the PSU, because that 4.4 volts undervolt condition would look like an overload.

At 11.4 volts, the 12 volt output is barely in tolerance.

The PSU should not be getting that hot. There simply is not that much load on it. I estimate (worst case):
CPU: 12 v @ 12 amps = 144 watts
Video card: 12 v @ 12 amps = 144 watts
RAM : 3.3 volts @ 6 amps = 20 watts
Motherboard: 5 volts @ 8 amps = 40 watts
The three drives: 5 and 12 volts totaling 60 watts

That's maybe 310 - 320 watts. These estimates are based on measurements I took with a lab calibrated (military lab) clampon dc ammeter on my Gigabyte P35 motherboard, Q6600 OC'd to 3.6 GHz running Prime95 on 3 cores and 3dMark on the fourth core, and a 640 MB 8800GTS.

I would dial back the OC until I figured out was happening.

 

[yonef]

OK, I made some stupid tests:
Installed back old PSU. Put a sheet of paper between CPU heatsink and the PSU. The temps stayed the same (46-47 C) on full load. The new PSU (without paper to block the cooler) manage to rise the CPU temps to 53-54C. This seem like not the air flow causing the heat
Is it possible new PSU to "manipulate" termal diodes on MB and causing them to report different readings?

 

[Dekasav]

This is the most interesting thing I've read all day.... too bad I have no advice.

Continue on!

 

[fahad9002]

Yonef Change Your PSU i think its faulty

 

[wilsonkf]

It is possible that the new PSUs adjust fan speed base on its own load - not the temperature.

Or its temperature for maximum fan speed is way higher than what you feel comfortable.

The best solution is to add a case fan to draw air near the CPU outside, or if you have one already, replace it with a more powerful one.

 

[yonef]

I do not need more powerful than 780W.
I already switched back to my old 600W noname PSU and everything runs very cool now. Every other PSU causes my CPU to run 10-12 C hotter.