New CPU overheating after replacement

radacadabra · Dec 18, 2017

Hello,

please ignore "new" in the title, everything in the PC is old

I replaced old Core 2 Duo CPU with "new" Core 2 Quad Q9400. I also replaced the coolers so new CPU stayed with its original Intel cooler, and I applied new thermal paste. Heatsinks are the same, so its height shouldn't be a problem. PC booted without a problem and recognized new CPU.

Afterwards, I checked the temperatures (with RealTemp): 36-44°C idle, but after less than 1 minute of Prime95 smallFFT stress test, temperature reaches 100°C and I manually stop the test. I tried putting the old cooler (from Core 2 Duo) - almost the same result, it takes him less than 30 seconds to 100°C

What could be the reason for this overheat? Bad cooler, or maybe some misstep in the assembly (I didn't change anything in BIOS)?

Some things that may be useful:

- same day, I added 2 GBs of RAM (ran memtest for 10 passes without errors) and replaced PSU (400 to 500 W, as PC didn't want to boot with 400)
- power socket in the motherboard next to the processor had 8 pin's in motherboard where Core 2 Quad initially was, and there are 4 pins now in the same place in my build
- yes, I plugged in the coolers and they are spinning
- no, I don't know the temperatures of the CPU in the build I took it from
- using Prime95 Blend test, it reaches 100°C in about 3 minutes before I stop it

TL;DR: can something else cause overheating of the CPU other than cooler+heatsink and thermal paste?

Thanks a lot in advance!

My build:

- motherboard: BIOSTAR P43-A7
- CPU: Intel Core 2 Quad Q9400 2.66 GHz
- RAM: 6GB DDR2
- GPU: ATI RADEON HD5770 Hawk 1GB

GhislainG · Dec 18, 2017

You wrote "Heatsinks are the same". Does the Q9400 cooler have a copper core? What thermal paste and how much did you apply?

radacadabra · Dec 19, 2017

GhislainG :

Thanks for trying to help.

Maybe I am using the wrong terminology. As heatsink, I meant the metal part between processor and cooler. Yes, the cooler has a copper core (old one didn't have). I used "Cooler Master IC Value V1" paste. As for "how much", I don't know exactly in grams

, but I applied an X on that metal part and didn't spread it. I did it like this in the past, and it seems well spread when I disassemble components.

GhislainG · Dec 19, 2017

Use the cooler with the copper core and apply thermal paste the size of a cooked grain of rice in the middle or spread it very thin using an old credit card or something similar. If that doesn't help, then check the voltage applied to the CPU or use a better cooler. The Q6600 came with a much larger cooler that was pretty good if not overclocking. Your CPU should reach nowhere close to 100°C running the latest version of Prime95.

radacadabra · Dec 19, 2017

I did your fist suggestion, nothing changed.
Could you please provide more info on how to check the voltages, or what to look for, and how can tampering with this lower the temperature? CPU-Z reports 1.088 core voltage, and its range from Intel is 0.850v – 1.3625v.
As for the better cooler option, I am trying to rule out all other options before getting one as I really don't feel like buying anything for build this old.

GhislainG · Dec 21, 2017

Try to lower the core voltage in the BIOS until the CPU no longer is stable; then increase it a bit and make sure stress tests don't fail. Are you sure the cooler that was provided with the CPU is the original one? If nothing helps, then you'll have to install a better cooler.

radacadabra · Dec 22, 2017

Thanks, I will try lowering the voltage later today and post an update.
As for the cooler, I am not sure that it's the original one. I do know that it is an Intel cooler with a copper core. That PC was custom built by some random guy, so there is a possibility that cooler was inadequate from the start.

UPDATE:
Cooler is the original one.
I am rethinking about lowering the voltage because cvolt is 1.088v and the range for that CPU is 0.850v – 1.3625v, and, from what I have read, the voltage should be a lot higher to cause overheating so I don't want to tamper with it unnecessary. Am I wrong/should I do it still?

GhislainG · Dec 22, 2017

There is a part number on the cooler; is it the one for the Q9400?

The Paladin · Dec 22, 2017

Normally I would suggest a clear of cmos on board and reboot and let it configure itself and try again.

Did you check;
1) the fan on your heatsink is connected to the CPU-FAN header on the motherboard?
2) it was running when you turned on the pc ? (visually see fan spinning)

radacadabra · Dec 23, 2017

Part number of the cooler is e21984-001. As far as I was able to find, that is the one for Q9400 and similar.

radacadabra · Dec 23, 2017

The Paladin :

As I wrote in the thread:
"- yes, I plugged in the coolers and they are spinning"

As for the clearing of CMOS, isn't that meant to solve problems for people who tampered with BIOS settings?

The Paladin · Dec 23, 2017

yes clearing the cmos is usually for bios problems but bios is what controls everything including the speed of your fans, clearing it cost nothing, and will permit a refresh of it, it may do absolutely nothing like it may solve the issue, I have seen systems where a cpu was changed and acted odd, temperature where odd, cleared cmos, rebooted goto bios and press f10 and voila all issues where solved. changing a cpu is changing a hardware component, and cmos maybe be acting out. it cost nothing do to and 2 mins to do it. and since you already tested fans, heatsink paste ect, your running out of options.

the only other thing that I find troubling is that you state "I tried putting the old cooler (from Core 2 Duo) almost the same result, it takes him less than 30 seconds to 100°C " which is indicative of a possible motherboard problem, you could pull the cpu and look inside the socket and see if your got bent pins. (looks like this) https://www.youtube.com/watch?v=1fkioojsxX8

marksavio · Dec 23, 2017

im not sure about older MOBOs but when you install a new CPU the BIOS will detect that its new and will reset some CPU settings and you have to press something like F1 to go to BIOS before you go into your OS on first install of the "new" CPU. to be on the safe side, you have to always reset CMOS tho. check your manual on where the jumpers are.

GhislainG · Dec 23, 2017

radacadabra :

It's the correct cooler; did you check how fast the fan spins at full load? If it spins lower than it should, check the settings in the BIOS. Also make sure the fan is connected to the CPU_FAN header.

radacadabra · Jan 16, 2018

The Paladin :

yes clearing the cmos is usually for bios problems but bios is what controls everything including the speed of your fans, clearing it cost nothing, and will permit a refresh of it, it may do absolutely nothing like it may solve the issue, I have seen systems where a cpu was changed and acted odd, temperature where odd, cleared cmos, rebooted goto bios and press f10 and voila all issues where solved. changing a cpu is changing a hardware component, and cmos maybe be acting out. it cost nothing do to and 2 mins to do it. and since you already tested fans, heatsink paste ect, your running out of options.

the only other thing that I find troubling is that you state "I tried putting the old cooler (from Core 2 Duo) almost the same result, it takes him less than 30 seconds to 100°C " which is indicative of a possible motherboard problem, you could pull the cpu and look inside the socket and see if your got bent pins. (looks like this) https://www.youtube.com/watch?v=1fkioojsxX8

I somehow missed your post. Thanks a lot for an explanation, but I actually just bought a new cooler and everything is great (stable below 50 °C under stresstest).

radacadabra · Jan 16, 2018

GhislainG :

Thanks, but I just bought a new cooler and got temps below 50 °C under load.

GhislainG · Jan 16, 2018

That's excellent.

New CPU overheating after replacement

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