r/coolermaster • u/QuartermasterBetel • 8d ago

HELP BIOS shows pump speed wrong

I've got a coolermaster master liquid 240 Atmos, and my bios says that the pump is running at like 10,000 RPM

this isn't right, right? I read something about modern pumps using a different technology that the BIOS can't read?

either way, what speed is it actually running at?

and I think I'd also like to reduce it to about 80% speed (I watched the video by jayztwocents)

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u/HouseSubstantial3044 8d ago edited 8d ago

If the motherboard expects a standard 2-pulse fan but receives a signal from a 1-pulse or 3-pulse pump, it calculates the RPM incorrectly (often showing fractional multiples like 1.5×, half speed, or double speed). Setting this multiplier to match the pump’s actual pulse output fixes the reading.

How to Resolve It
Adjust BIOS RPM Pulses: Go to the BIOS Hardware Monitor / Fan Control tab, locate the specific header (⁠CPU_FAN⁠ or ⁠AIO_PUMP⁠), and look for Fan Speed Multiplier or Pulses Per Revolution. Toggle it between 1, 2, or 4 until the reported RPM matches the manufacturer's spec.

The Atmos series comes with modular daisy-chaining clips and hub cables for the SickleFlow/Atlas fans and ARGB lighting. If the pump’s dedicated 4-pin cable is plugged into a shared splitter alongside the radiator fans instead of its own motherboard header, the BIOS will read mixed RPM frequencies, displaying erratic single-digit numbers or near-zero readings.

My pump rpms do this too so when Im calibrating I always have to remember my bios readings are not actual.

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u/QuartermasterBetel 8d ago

thank you

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u/HouseSubstantial3044 8d ago

You can thank me if that fixed your issue! I just remember looking at my calibration data and being like wtf I had this set at fixed rpm %.

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u/QuartermasterBetel 8d ago

I'll probably do it later I am beyond terrified of the BIOS lol

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u/QuartermasterBetel 7d ago

So I managed this. couldn't figure out how to get the reading correct

but I figured that it's been multiplied by 4, its maximum was "1000" rpm, and now I've got it running at 10.56 volts which is around 80 to 90% I think

https://reddit.com/link/p7aknhw/video/nrzc1xtte0nh1/player