CPU fan RPM over rated speed

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jordan1794

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Dec 21, 2014
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Hello all, I have a 4790k at stock speed(turbo to 4.4Ghz)
Cooling it is a Phanteks PH-TC14
Today I ran my first Prime95, and ended up with a max temperature of 77
(Temperature peaked within 2 minutes, then stayed steady for the next 8 minutes before I ended the test)

But my CPU fan displayed as running at over 1600 RPM, when it is only rated at 1300.
However the CPU fan is actually two fans, connected with a Y adapter.


So my questions are:
1.Is my CPU fan being pushed wayyyy too hard by my MOBO?
2.Is my CPU fan just far outperforming the rating?
3.Is my system reporting an incorrect RPM?
4.Is the system reporting double what my RPMs actually are, because the voltage is doubled to run to two fans instead of one?
5.If number 4 is the case, then that should mean at the peak stress test, my fans were only running at about 60% power, which would leave quite a bit of room for overclocking, right?
(I don't really plan on overclocking yet, just want to have a good understanding of what's going on)

temperature%20test_zps0clutij9.png
 
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H


That's exactly what you want. You have a properly made PWM splitter cable. One of the two fan connectors on the Y-cable is missing the third pin. The third pin is the TACH RPM wire from the fan that tells the motherboard how fast the fan is turning. You can only have ONE fan reporting speed to a fan header, so they remove the third pin from one of the two fans to make sure it's not screwed up.

Honestly, everything looks great. You've got a terrrific cooler. You've got hooked up perfectly right with the properly made y-cable supplied with the cooler. Your fan speeds look good...
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hwc1954

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Jan 7, 2015
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I don't think it's at all unusual for fans to run faster than their rated specs. I have some 1600 rpm Noctua fans that run 1800 rpm wide open.

It's an imprecise measurement. The voltage from each motherboard is going to be a little different Each fan is going to be a little different.

 
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photonboy

photonboy

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Jun 20, 2006
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1) The rating is 1300 + or - 10% meaning it shouldn't exceed 1430RPM. With the ADAPTER it's 1200RPM+/- so shouldn't exceed 1320RPM.

2) The fan uses PWM not voltage so it's pretty accurate.

3) I doubt the fan actually ran over 1600RPM. I suspect it's an issue with how it's measured or how it's being reported.

*UPDATE*
You said you're using the adapter?
The specs say it's "not meant for 4-pin fans" but says it's a PWM adapter. That makes no sense since all PWM fans are 4-pin. Not sure what's going on there.

 
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jordan1794

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Dec 21, 2014
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Yeah, popping the plugs off just added more confusion...
On the Y adapter it has 4 pins plugging into the mobo.
On the other end one of the plugs has 4 pins, the other only has 3.
Both of the fans are 4 pin...


What would be the issues with plugging the second CPU fan into the cpu_opt for (I've heard its for water cooling, but will it work for a secondary cpu fan?)

Would I be better off running one fan plugged into the CPU fan spot on the mobo, then plugging the second fan into a system plug, then set it in BIOS to run at max? I know on case fans running them max all the time doesn't really hurt them, but idk about the cpu fans...
 
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jordan1794

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Do you think my mobo is reading the incorrect speed, or just the HWMonitor?
 
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jordan1794

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So I'd just like to update this, I plugged the two fans directly to the motherboard and circumvented the Y adapter.
(Plugging one into CPU fan and the other into CPU_OPT)

The fans are running the exact same way, except that now I can see both the RPMs (Still going to 1600+ during the stress test)

I don't even know anymore, I was gonna call Phanteks to ask them, but I'm not sure it's worth it...I mean everything is working fine...

Then again, I'm so curious lol.
 
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hwc1954

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Jan 7, 2015
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That's exactly what you want. You have a properly made PWM splitter cable. One of the two fan connectors on the Y-cable is missing the third pin. The third pin is the TACH RPM wire from the fan that tells the motherboard how fast the fan is turning. You can only have ONE fan reporting speed to a fan header, so they remove the third pin from one of the two fans to make sure it's not screwed up.

Honestly, everything looks great. You've got a terrrific cooler. You've got hooked up perfectly right with the properly made y-cable supplied with the cooler. Your fan speeds look good. Just think about it this way: you got an extra special fan with bonus performance! :) It's certainly not going to hurt anything. It just gives you a little more cooling potential.

Keep in mind, the rated fan speed is for a single fan. You've got one fan that is, essentially pushing air into a second fan and making it turn faster. If you unplugged one fan, it would still be turning just from the air flow. Not surprising that the pair of fans runs faster than one by itself.

Look at the right hand column of fan speed gauges below. See the third one down, the PSU EXHAUST FANS running at 1882 RPM? That's a Noctua rated at 1600 rpm max speed. This is also a PUSH/PULL pair of identical fans.

aquaero_load_zpsgobysdlb.jpg


 
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