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 Post subject: NH-L12 for an Intel 65 W CPU
PostPosted: Thu Feb 14, 2013 9:58 am 
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Joined: Thu Feb 14, 2013 9:24 am
Posts: 10
I have bought the low power i7-3770S version CPU. This runs at 65 W TDP instead of the normal 77 W. My thought there is that if the maximum TDP is lower, then the maximum cooling that is required will be less, and thus less noisy. I understand that under idle or light load the differences may be small.

The Noctua support team recommended the NH-L12 for my CPU, so of course I ran over to SPCR to look for a review :) see http://www.silentpcreview.com/article1261-page6.html

I have two questions.
The review used a 95W AMD CPU, while I have a 65 W Intel CPU. Assuming the same airflow / fan speed, how do I get a rough guess for what the temperature rise will be when going from the 95W CPU to my 65W CPU? I am particularly interested in the top table, where the 6V row that shows both stock fans at a combined 12 dBA allow just a 22 degree Celsius rise (with 95W CPU). What range of Celsius degree rise would I likely see with the 65W CPU at the same fan power/noise level?


My other question is, what is good enough? I know Intel says maximum temperate is 69.1 degrees C for the i7-3770S. Even with the 95W CPU, the review listed above shows that at 12 dBA and CPU load only a 22 degree rise is seen, so say an absolute temp of 45 degrees (with 23 degree ambient temp). I also think it is curious that some reviews show a 95W CPU with the same cooler going up to 59 degrees. Not sure what to think of the difference in results.
Anyways, the question is: Is 45 degrees absolute temp good enough, given that I intend to keep this computer for 10 years? Is 59 degrees good enough? (I kept my last computer for 10 years.) How low should I aim to keep the CPU temperature when it is under full load, for CPU longevity?


Okay, and a third question: Down-flow CPU cooler: How valid is it to think that having a down-pointing CPU cooler will help the longevity of the motherboard? I am getting an ASUS P8Z77-M PRO.


My usage patterns: Right now, pretty light. But I do software development, and as I plan to keep this computer a long time, I prefer to overbuy than to have to put up with excessive noise.

Thanks guys! I will appreciate your help.


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 Post subject: Re: NH-L12 for an Intel 65 W CPU
PostPosted: Thu Feb 14, 2013 8:21 pm 
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Joined: Fri Aug 05, 2005 3:29 am
Posts: 1131
Location: UK
The Asus P8Z77-M Pro has excellent BIOS fan controls which can be monitored or supplemented by Fan Xpert+. Fan Xpert+ is part of AI Suite II, a free download from the Asus website. If your priority is quietness, all you need do with this motherboard is to set the CPU fan profile in the BIOS to Silent. As the Noctua 120mm PWM fan supplied with the NH-L12 fan has a speed range of 300 to 1500 rpm you also need to change the CPU fan speed low limit setting. By default it is 600 rpm, it needs to be set to Ignore. The Silent profile will keep the PWM duty cycle down in the 20% range until the CPU reaches around 40C. Only then will it begin to elevate fan speeds. The CPU temperatures you will see in practice will depend on how much system load is generated. Typically only CPU intensive video utilities or heavy gaming use are likely to produce significantly high processor temperatures. It is easy to monitor the BIOS settings and CPU temperature with the graphic display in Fan Xpert+. If temperatures are not to your liking another BIOS fan profile can be selected if required and there is the option to create a manual profile both in the BIOS and with Fan Xpert+.


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 Post subject: Re: NH-L12 for an Intel 65 W CPU
PostPosted: Thu Feb 14, 2013 9:13 pm 
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Joined: Thu Feb 14, 2013 9:24 am
Posts: 10
Thanks lodestar. Yes, I am looking forward to playing around with FanXpert and seeing actual temperature values. Especially as you indicate it is quite flexible.
Unfortunately I am trying now to determine what cooler to buy, without having a chance to see how it works with a 65W CPU, so I do not have adequate information. But I think I'll proceed with the NH-L12 and see what happens.


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 Post subject: Re: NH-L12 for an Intel 65 W CPU
PostPosted: Thu Feb 14, 2013 9:20 pm 
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Joined: Thu Oct 06, 2005 4:36 am
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Location: Monterey Bay, CA
1) A cooler's thermal performance is fairly linear at a given airflow. So, if a CPU is consuming 95W and the cooler has a 22C rise, then it's thermal impedance is simply 22C/95W = 0.232 C/W. So, for 65W load, the temp rise at that same airflow would be close to 65*0.232 = 15C.

2) I don't think you'll have an issue with temperature. Really, don't worry about it unless you start seeing >>65 C while running your typical programs..and that's probably an indicator of a poorly seated heatsink.

3) Airflow over the VRM circuitry is a positive thing...but probably not neccessary given your low TDP CPU. Lower VRM temps = higher efficiency.

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1080p Gaming build: i5-4670K, Mugen 4, MSI Z87-G45, MSI GTX 760 2GB Gaming, 8GB 1866 RAM, Samsung Evo 250GB, WD Red 2TB, Samsung DVD burner, Fractal Define R4, Antec True Quiet 140 (2 front + rear) case fans, Seasonic X-560. 35-40W idle, 45-55W video streaming, 170-200W WoW, 200-230W Rift, 318W stress test (Prime95 + Furmark)


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 Post subject: Re: NH-L12 for an Intel 65 W CPU
PostPosted: Thu Feb 14, 2013 9:33 pm 
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Joined: Thu Feb 14, 2013 9:24 am
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@CA_Steve: Thanks for the info; I appreciate it.


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