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Sped up fans and CPU temp went UP?

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August 29, 2008 10:00:46 PM

Hello all:
I just switched cases from an old Antec SLK3800 to an Antec Three Hundred which is supposed to be be good at keeping the components cool. I have installed two 120mm fans in the front (running at low) and the drive temps for my 6 hard drives is fine. The Nvidia 7600GT graphics card hasn't risen above 59C for my typical uses.
BUT the CPU temps for the Intel Q6600 quad-core are higher than they were in the old case. I used to see 42-47 at idle and most of the time it didn't rise above 54C. With this new case I am seeing 50-52 at idle and up to 59C with heavier use such as transferring 40 or 50 GBs of recorded tv to a different drive while watching a tv show in Media Center and surfing the internet.
I was disappointed in the higher temps so I decided to turn up the speed on the case fans. This case has a 120mm rear fan and a 140mm top fan right above the cpu. When I turned up the speed from low to medium on both fans the temps immediately went up about 5C on the cpu but the drives dropped a couple degrees on each one.
I am confused that the temp went up instead of down and wondered if the close proximity of the 140mm fan to the cpu fan is sucking air away from the cpu fan and preventing it from blowing down onto the cpu correctly. As soon as I reduced the speed back to low on the top fan the temps went back to the original temps. I really don't think I should need to install some big aftermarket fan to replace the stock Intel fan/heatsink but really need help figuring out why the faster top case fan speed heats up the cpu???????

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August 29, 2008 10:41:27 PM

One reason why the temps go up, is distorted airflow. Turning the fans up, depending on how they are positioned, can cause vacuum lock (pocket hot air) then provide cool air, like you mentioned about the 140mm fan and rear 120mm fan.

So having fans really close together at high rpms can cause temps to go up. Try just experimenting what may work best. Like turning the top fan on low, and rear high or vise versa till you find some kind of airflow that works for the stock HSF better.

I personally use a ZeroTherm NV 120 in an AeroCool Engine PC case that has less fans then 300 (doesn't have a top 140mm fan for example) and I still get idle temps of 28-30C tcase, or 30-40C average cores idle, depending on the ambient temp which would be the biggest factor on temps.
August 29, 2008 11:10:15 PM

I agree with Grimmy. Play around with it. Make sure the wires from the power supply are not blocking the air flow. I would say set the front fans to low and the rear and top fan to high. I have a case with one 120mm in the front and one 120mm in the back that run pretty slow, plus the PS fan and I never have temp problems. I heard the Q6600 can run a little hot so an aftermarket cooler might not be a bad idea. But before spending cash try playing around with it. My CPU runs around 46C idle.
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August 29, 2008 11:28:02 PM

Grimmy said:
One reason why the temps go up, is distorted airflow. Turning the fans up, depending on how they are positioned, can cause vacuum lock (pocket hot air) then provide cool air, like you mentioned about the 140mm fan and rear 120mm fan.

So having fans really close together at high rpms can cause temps to go up. Try just experimenting what may work best. Like turning the top fan on low, and rear high or vise versa till you find some kind of airflow that works for the stock HSF better.

I personally use a ZeroTherm NV 120 in an AeroCool Engine PC case that has less fans then 300 (doesn't have a top 140mm fan for example) and I still get idle temps of 28-30C tcase, or 30-40C average cores idle, depending on the ambient temp which would be the biggest factor on temps.


Thanks for the input Grimmy. I naively thought Antec put the huge 140mm case fan an inch above the cpu to make the cooling more effective LOL! I guess the cooling of my old case was helped a lot by having a case side vent with a funnel that directed fresh air to the top of the cpu fan/heatsink. When I looked at the pics of the Antec Three hundred case I thot the side vent was located over the cpu and instead it's above the graphics card. My mistake for not checking more carefully. I wish Antec still made a case like the SLK3800 but had room for 6 hard drives like the Three Hundred.
August 29, 2008 11:39:11 PM

caamsa said:
I agree with Grimmy. Play around with it. Make sure the wires from the power supply are not blocking the air flow. I would say set the front fans to low and the rear and top fan to high. I have a case with one 120mm in the front and one 120mm in the back that run pretty slow, plus the PS fan and I never have temp problems. I heard the Q6600 can run a little hot so an aftermarket cooler might not be a bad idea. But before spending cash try playing around with it. My CPU runs around 46C idle.


Hi caamsa

I appreciate your input. I may have to go to an aftermarket cooler at some point. I have a Core2 Duo E8400 in another pc and it does run a lot cooler than the quad-core even though it's running at 3 GHz vs the 2.4 of the quad-core. I kinda hate to run any of the fans on high because the pc is in my bedroom and it comes on at all hours of the night to record tv shows and would probably disrupt my sleep! I'm going to try setting the two front fans at medium instead of low and see if maybe they'll be able to keep up with the volume of exhaust air the two larger fans are moving. Thanks again.
August 30, 2008 12:14:47 AM

I think I figured out why the cpu temps are running higher in the new case.......I was using Intel onboard graphics before moving to the new case and added in a discrete graphics card which is probably adding quite a bit of heat to the case interior. Also, I went to a bigger psu and it is on the bottom of the case and more of the heat probably rises up to the cpu than it did with the old top-mounted psu.
August 30, 2008 12:25:54 AM

and what video card is it?

A video card will or can run hotter then the CPU. I use an 8800GTS 512MB card, with the fan on auto, can reach past 70C. I can manually turn the fan speed up, but it uses a air cooling by forcing heat out of the 2nd PCI slot.

This would be different if the video card uses passive, or a fan that moves air around the lower part of the PC case. In that case you would need to work on airflow on the lower part by either forcing air out, or if you have poor intake, forcing air in on the side.
August 30, 2008 12:26:20 AM

newnerd said:
I think I figured out why the cpu temps are running higher in the new case.......I was using Intel onboard graphics before moving to the new case and added in a discrete graphics card which is probably adding quite a bit of heat to the case interior. Also, I went to a bigger psu and it is on the bottom of the case and more of the heat probably rises up to the cpu than it did with the old top-mounted psu.


from my personal experience, the 7600GT heats up a fair bit. and believe me, adding a video card can really increase your case temps. after i installed my 4850, the temps skyrocketed.
August 30, 2008 12:33:57 AM

For like the 7600GT, I see it uses a fan to move the air around the bottom part. have a fan to force air out of the side can help, or it could make it worse depending on how good the intake is from the front.

Or you could have airflow from the side in, with something that can help extract hot air on the bottom with something like (just an example):

August 30, 2008 9:55:46 PM

I tried increasing the 2 front fan speeds from low to medium and can't tell if it really made a difference. I then increased the rear fan to medium and it seemed to be about 2C lower........hard to say for sure. Then I tried increasing the top 140 mm fan to medium and I think that brought the temps down about 2C more. At that point it seemed to be running about the same temps as my old SLK3800 case......low 40's at idle, high 40's with normal use and mid-fifties working quite a bit. This is satisfactory to me but I don't like the added fan noise. It's not bad when I'm using the pc and have music or tv going but when it wakes up from sleep to record, it'll probably wake me up too! If that becomes a problem I may just go back to the intel onboard graphics and remove the 7600 GT OC graphics card.

I think the tv picture was better with the onboard graphics than it is with the add-on graphics card but I have a couple of games we play occasionally and will have to use a different pc for them I guess.

Another option might be to get another ATI Radeon HD3600 graphics card. The one I have in another pc runs about 20-25 degrees cooler than the 7600 GT OC and the tv picture is much, much nicer. Perhaps drop in heat output from the graphics card will make a big difference. There's not a lot of open space in this case with 6 H.D.s, 2 Optical drives and all the necessary cables.

Thanks a lot to everyone for their suggestions. I feel reassured that my cpu fan/heatsink are not the main problem. I always wonder when I install one of those Intel push-pin fan/heatsinks if I really heard them click into place LOL!
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