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Increasing Fan Speed has NO EFFECT on Temps

post #1 of 5
Thread Starter 
I've made some interesting observations with my cooling setup in the present sig rig. During some recent fan swapping experiments, I've observed that, no matter which fan I have mounted on the heatsink, my CPU's core temperatures don't seem affected by changes in fan RPMs. Whether at "idle" or at full max load, changing fan speeds with a manual fan controller doesn't appear to affect the cooling power of the heatsink.

For example, given an ambient temperature of 25 degrees C, the CPU with minimal load will register core temps of 34 - 35 degrees C (Core0 & Core1, respectively); at full Orthos load, the highest spike temperatures registered are 51 - 48 degs C (Core0 & Core1, respectively). Given these conditions, changing fan RPMs doesn't change either the minimal load nor the max load temps registered at all; the only observable effect is an increase in fan noise.

Temperatures were observed using Everest Ultimate.

Has anybody ever had similar experiences to this? Can anybody offer any possible explanations for what I've observed?

Many thanks up front!
    
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post #2 of 5
Are the idle temps the same as well with different fan speeds. I guess all that really matters are the load temps, but maybe you've reached the limit of your heatsinks cooling potential. Have you experimented with a push-pull set up?
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post #3 of 5
Thread Starter 
Quote:
Originally Posted by jaclipse View Post
Are the idle temps the same as well with different fan speeds. I guess all that really matters are the load temps, but maybe you've reached the limit of your heatsinks cooling potential. Have you experimented with a push-pull set up?
My observations indicate that the idle temps (as well as the max load temps) are more influenced by the ambient temperatures than anything else. Of course, if I turn the fan fully off, the temperatures rise more than if the fan (any of the fans I've been testing) was on.

I should added that I'd observed this behavior with both the Thermalright SI-128SE presently mounted, and a Thermaltake Big Typhoon. The fans being tested include a Thermaltake 120mm x 25mm, a Panaflo 120mm x 38mm 103CFM monster, a Delta 120mm x 38mm 110+CFM, and a Delta Tri-Blade 120mm x 38mm (140CFM).

More information: The fans all respond to the fan controller, for sure. And the fan controller delivers full available power to the fans when set to max (i.e., with the Tri-Blade Delta, the RPM peaks at around 3400RPM, per Everest Ultimate).

Note: Push-pull is not possible with either of these heatsinks (without massive modifications, anyway).
    
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post #4 of 5
My temps go from 35-35-30-30 in normal use to about 38-38-33-34 on low fans.
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post #5 of 5
Thread Starter 
Update: I've been testing my rig, and it seems that changing fan speeds does influence the temperatures. The effects, though, aren't as pronounced as you might expect.

To wit, at 0 RPMs on the Delta Tri-Blade 120mm x 38mm, the temps are peaking at 53 degs C at the cores; at 1500~RPMs, the temps are down to 48 degs C at the cores; at 2100~RPMs, a further decrease to 46 degrees C; at the fan's full speed of circa 3700RPMs, the temps register best figures of 44 degs C.

For the record, the ambient temperature during these test runs was at 23.4 degs C; CPU load temps were generated by Orthos Small FFTs; TIM used was AS5 on a bare die.

Thanks to all who offered ideas (which motivated me to test more carefully, also).
    
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