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IDProjectCategoryView StatusLast Update
0001958SpeedFanFan controlpublic2012-03-16 09:53
Reporterroesti91 Assigned Toalfredo  
Status acknowledgedResolutionopen 
Platformwin7x64OSx64OS Versionlatest
Product Version4.46 beta 
Summary0001958: Hysteresis not working in adv. fan control
DescriptionHysteresis not working properly in adv. fan control due to BIOS fan speed overwrite?
Steps To ReproduceI programmed the 0% fan point at 55C. The 56C point is at 34% fan speed. (34% is the min. required for the fan to still operate). My hysteresis is set to 10C. I now expect the fan to shut off at 56-10=46C, but is shuts off at ~50C and then comes back (at once) on until I reach the 46C. What I guess is happening is that the BIOS fan control cuts the fan at 50C and speedfan has to put it on again until it goes lower than 46C.
TagsNo tags attached.
Motherboard ModelL502X
Video Card Model540M



2012-03-16 08:59


debug.nfo (139,516 bytes)


2012-03-16 09:18

manager   ~0006891

If your fan speed is automatically set to, say, 40% at 35C, it will not be further decreased until (35C-hysteresis) is reached. IMHO, a 10C hysteresis value is a bit too large.
You should check to see when SpeedFan has actually "changed" the PWM value because the hysteresis is applied to that value.
That said, the BIOS might be interfering.


2012-03-16 09:27


hysteresis.png (7,436 bytes)   
hysteresis.png (7,436 bytes)   


2012-03-16 09:36

reporter   ~0006892

Well, I dont think the PWM is actually working well on the DELL laptop. 34% is the min. where fans still spin, the next higher spin is reached at 0000019:0000070% and then 100%, so there are 3 steps rather than a proper PWM ramp ... :-(

Beside the PWM value is dropped from 34% to 0% (in a single step) once 46C is reached: Exactly as advertised by my curve.

I attach the curve I programmed for this above. The question remains: How do you stop the BIOS interference so the Hysteresis works properly?


2012-03-16 09:42

manager   ~0006893

I see that you have a DELL where only the DELL interface is working. Since it allows only for 3 different levels, you can't rely on a fine grained control. You should be aware of the hardware limits of fan control on your system and find the way to get the best out of it.


2012-03-16 09:53

reporter   ~0006894

Last edited: 2012-03-16 09:53

Thank you. I really hope the mouse issue is resolved soon, otherwise speedfan cannot be used at all on those DELL laptops:

Issue History

Date Modified Username Field Change
2012-03-16 08:59 roesti91 New Issue
2012-03-16 08:59 roesti91 Status new => assigned
2012-03-16 08:59 roesti91 Assigned To => alfredo
2012-03-16 08:59 roesti91 File Added: debug.nfo
2012-03-16 09:18 alfredo Note Added: 0006891
2012-03-16 09:18 alfredo Status assigned => acknowledged
2012-03-16 09:27 roesti91 File Added: hysteresis.png
2012-03-16 09:36 roesti91 Note Added: 0006892
2012-03-16 09:42 alfredo Note Added: 0006893
2012-03-16 09:53 roesti91 Note Added: 0006894
2012-03-16 09:53 roesti91 Note Edited: 0006894