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MB vs. CPU Cooling

Last response: in Motherboards
September 4, 2009 6:54:30 PM

So, I upgraded my computer yesterday and am having some cooling issues. I have a 2 year old thermal take black armor case. It has a fan on top that blows OUT, two fans in back the blow OUT, and one fan in front that blows IN across the hard drives.

I installed a new Asus P6T deluxe V2, with a 920 I7, 6GB of G.Skill DDR3 (currently at 1033, OC'able to 2k), an EVGA 8800GTS dedicated to physics & an EVGA 275 GTX. I'm using the I7 stock heatsink & fan. I have a 750W OCZ gamerextreme SLI ready PSU.

It's running HOT. Idle CPU temp is ~ 50C, MB temp is ~ 52C. Light load, CPU temp is ~ 53C, MB temp is ~ 55C. Under a heavy load, CPU temp is ~ 62C & MB temp is ~ 60C.

Note: I had Microcenter do a post test on the cpu/mb. They installed the CPU, I haven't tried reseating it or checking IT yet.

So, I have a few questions:

1. The MB temperature sensor measures the ambient temperature inside the box, yeah? I'm not sure where that sensor is, but if it's directly under the GPU or something like that, could it be inacurate?

2. Is there a direct link between the CPU temp & MB temp? If microcenter used some crappy thermal paste & the stock heatsink sucks, then would installing an aftermarket heatsink & using some AS5 solve both the CPU & MB heating issues?

3. I've never attempted to test the efficiency of my fans before. When I put my hands in front of them, I could BARELY feel air flow. In order to accurately test that they were working, I had to put a thin paper receipt in the direct line of air flow and watch to see if it moved.

3.1 Is it possible that the fans have gone bad over 2 years? Should I replace them?
3.2 Is it possible that this new equipment is trying to draw too much power for my 750W PSU? Is it possible to test this?
3.2 What are my best options for getting the temp down? I haven't overclocked anything yet, but I can't wait to - but obviously I need the stock temps waaaay down first.

More about : cpu cooling

a b à CPUs
a b V Motherboard
September 4, 2009 8:38:46 PM

First off, have you checked your temps with the side of the case open, does this change them? Try running your computer open, with a desk or box fan blowing directly onto the motherboard (don't put the fan right in there, but close enough to hit the computer with most of the air). If this improves your temps, you have an airflow issue in the case. If this doesn't improve your temps, you probably need a better CPU cooler.

1) I think MB temperature is usually the temperature of the board, usually beneath the CPU socket It is not the ambient air temperature in the case.

2) I think improving your CPU cooling should also reduce MB temps, as the CPU would radiate less heat onto the board. You can also try to direct more air across the on-board components like voltage regulator and northbridge heatsinks.

3.1) Yeah, fans can go bad, they can get clogged with dust or lose lubricant and slow down. You should definitely be able to feel the air your fans are moving. Simple question: are there dust-screens attached to your fans, do those just need cleaning?

Try pulling the fans from the case and running them (unplug your HDDs, turn on the computer) and see how much air they blow all by themselves. If they still feel week out in the open, they are bad (or just weren't that good to begin with). You can try replacing them, see if you get more airflow out of the new ones.

3.2) You can check what your voltage levels are using some Asus software or other utility. If your voltages are too high or low it could indicate a problem. However, 750W should be sufficient for your system.

3.3) If you want to overclock, use an aftermarket cooler. Also check the northbridge cooler while the computer is on (i.e. touch the heatsink). If it feels hot to the touch (almost painful), you definately have a cooling issue.
September 4, 2009 8:48:16 PM

Awesome, thanks for the tips dude. I did run the computer with the side case off as well. This did not change the results at all, which, as you said, may indicate a problem with airflow and possibly the fans.

There are dust screens on the fans an I did clean them while I was installing all the new components. PCProbeII shows that they're all spinning at around 1500RPM.

I think tonight, before anything else, I'm going to clean the proc, apply some new AS5, and reseat it.

As far as the fans go - if they are powered directly off the molex connector, they should be spinning at max speed all the time, right? The fans that are plugged into the mobo however, do have their speeds controlled, yeah?
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a b à CPUs
a b V Motherboard
September 4, 2009 8:56:55 PM

Re-seating the CPU cooler is a good idea.

As for fan power, using molex should mean full-power. Usually, case fans are not speed-controller, even when plugged into the motherboard. Usually, the motherboard only controls the speed of the CPU fan.
a b à CPUs
a b V Motherboard
September 4, 2009 9:19:56 PM

F4RR4R said:
Under a heavy load, CPU temp is ~ 62C & MB temp is ~ 60C.
Which CPU temperature is that, the cores or the case (heatspreader) temperature? Either way, it doesn't seem like a particularly bad temperature for a fully loaded CPU.
September 4, 2009 9:32:02 PM

I'm using the Asus PCProbeII Utility. It has two temperature values, one labeled CPU & one labeled MB. I assume that they refer to the temperature sensors located on the processor (or right below it on the MB) and a on the motherboard (on the P6T, I believe this sensor is down by the northbridge).

Edit: Did a little reading on the MB sensor. Seems it's meant to monitor the northbridge temperature. Isn't 60C waaaay to hot for the northbridge?

And more reading states:
You 'motherboard' temperature is being sensed by a thermal diode located behind PCI2 and the temperature reflected is caused by your video card... Raise the probe alarm threshold to 70c.
September 5, 2009 12:59:53 AM

Wow. Cleaned off the proc & heatsink w/ some isopropyl, applied a lil' AS5, reseated the heatsink ... and voila! CPU is now running idle at 38c. MB temp is lower now as well, though not as low. I'm pretty sure the articles that said the MB temp sensor is right below the GPU is acurate, because it's heating up directly in coorelation with the GPU stress, while the cpu is staying cool.