However all of this is a product of me not realizing thereare multiple ways to change fan speeds, A-Tuning, a Windows program which hadto be downloaded from the APP shop  anddescribed briefly in Chapter 3.2 of the H270M motherboard manual, and on the EZMode  screen with theoption of Silent, Standard, Performance, and Full Speed and a third, under Chapter 4.8"Hardware Health Event Monitoring" with selection of Fan-Tastic Tuning- with almost identical options andscreens as the same feature in stand alone A-Tuning with the same name on its tab.  They all are integrated but the manual is notabout to divulge.

So what I have learned by trial and error is that I cancontrol  my three pin chassis fans by modifying the curves in either the UEFI or A-Tuning.  Custom curves generated inA-Tuning are transferred or even use the same code fields in the UEFI and visa versa.  Maybe someday I will figure outthe relationship between the suggested curves stored in the UEFI as Silent,Standard, Performance and Full Speed and those in A-Tuning called PerformanceMode, Standard and Power Saver.  I still get period rpm blips (about double the value) for the two chassis fans and must assume this is a product of the signal sent from those two fans since I do not see it with the CPU (and both use the same principle sending down the third pin). 

Some preliminary data suggests that the stock fan suppliedwith my i5-7500 is marginal at best but I have yet to push the chip and I went into this knowing that would be an eventual upgrade.

I am disappointed there is no detail on the code logic of these two implementations of what is obviously the same basic code but with slightly different external interfaces but not worth the hours of trial and error to right a manual update.

I?�ll annotate Persec's  questions:

First the Intel stockCPU cooler. I assume it is connected to the CPU_FAN1 connector at the top ofthe board. If you run the FAN Test in A-Tuning on the CPU_FAN1 selection, doyou get a full range (10% - 100%) of fan speeds? Meaning at 10% the RPM is notzero and the speed is below 1,000 RPM?

 Yes, connected to the CPU_FAN1, a four pin female connectedto a four pin female.  The FAN-Tastictests show range from ~1000 rpm at 10% to ~3100 at 100% and this has been reproducible.  However System Info shows the temp around 30Cand yesterday it was running about 2200 reasonable, but today saw it at 3200,then later 2200 and now 1050 all at Standard. So the curves appear reproducible but not the running speed.  I did set to Full Speed in the BIOS and itjumped to 3200 after I rebooted and back to 2200 when I again changed andrebooted.   

When the Intel Skylake processors were released (Iknow you have a Kaby Lake CPU) we discovered that certainmodels of the Intel stock CPU cooler (Delta on the fan's label) weredefective. 

To many peculiar data points here to draw any conclusionyet.

Next the two Corsair case fans. You have them connected directlyto the mother board CHA_FAN1 and CHA_FAN2 connectors,right? Do those two fans have standard three pin fan connections? I ask becausesome Corsair case fans in the past have had proprietary connectors for thebuilt in fan speed controller.

Definitely connected to CHA_FAN1 and 2.  Apparently they have changed their connectors.  The connectors are three pin and with a slotin their side so that they can only connect to the board?�s four pin femalecovering pins 1 to 3 which has a projection to assure.  They come with an option to connect to athree speed control switch on the back of the case getting their power from anSATA power connection and therefore I know they are controllable by varyingvoltage on I assume pin 2.  My H270Mboard is supposed to do the same as I read the specs.

If you run the FAN Test in A-Tuning onthe CHA_FAN1 and CHA_FAN2 connectors, with the Corsair fans, do you get a fullrange of fan speeds, from 10% to 100%? If you do then the fans are beingcontrolled correctly by those two fan connectors.

Here is where the problem gets out of hand.  The FAN tests are not consistent.  Run once yesterday and thought they appearedreasonable but today have repeatedly run tests on each fan.  Max speeds have been mostly around 1500 withone 1700 but 10% has run from 0 to 7000 and other low percentages have shownspurious large numbers has high as 6000. Very screwy and not reproducible. I would not even believe my memory except I have been taking screencaptures.

I?�ll leave this response at that admitting I have not attemptedto adjust the curves using A-Tuning. However I did try modifying using the BIOS and set to Full when I waschecking out the CPU Fan.  However forthe case fans there was not change ??they stayed at their 1100/1200 readingpopping to 2200 for a few seconds every 10 to 15 seconds.  I would like to do some testing underA-Tuning but appreciate clarification when changes made here apply, i.e whatdoes ?�Auto apply when program starts, ??i.e. an option at the bottom of theFAN-Tastic Tuning window ??if you start and stop the program or upon a reboot?

For the record I am loving this computer just for its speedin rebooting and handling the loading of the everyday programs I use.  Once I get this problem settled will have toquantify this judgment.