it8716: rpm too high

[ticket]

Gigabyte M56S-S3 board AMD X2 BE-2350 CPU

it8716 module shows too high rpm count for case fan, which is a lownoise (slow) Papst 8412 N/2GLE, specced at 1500 rpm:

#  sensors
k8temp-pci-00c3
Adapter: PCI adapter
temp1:        -9°C
temp2:       -21°C
temp3:       -18°C
temp4:       -14°C

it8716-isa-0290
Adapter: ISA adapter
VCore:     +0.99 V  (min =  +0.00 V, max =  +4.08 V)
VDDR:      +1.89 V  (min =  +0.00 V, max =  +4.08 V)
+3.3V:     +3.30 V  (min =  +0.00 V, max =  +4.08 V)
+5V:       +4.84 V  (min =  +0.00 V, max =  +6.85 V)
+12V:     +11.97 V  (min =  +0.00 V, max = +16.32 V)
in5:       +3.18 V  (min =  +0.00 V, max =  +4.08 V)
in6:       +0.10 V  (min =  +0.00 V, max =  +4.08 V)
5VSB:      +4.92 V  (min =  +0.00 V, max =  +6.85 V)
VBat:      +3.04 V
CPU Fan:   798 RPM  (min =    0 RPM)
Case Fan: 11250 RPM  (min =    0 RPM)
temp1:       +36°C  (low  =  +127°C, high =  +127°C)   sensor = thermistor
temp2:       +35°C  (low  =  +127°C, high =  +127°C)   sensor = thermistor
temp3:       +25°C  (low  =  +127°C, high =  +127°C)   sensor = diode
vid:      +1.000 V

The case fan rpm is increasing. cpu fan is stable.

[khali]

What fan speed values does the BIOS show?

Please attach the output of the following command (after unloading the it87 driver):

isadump 0x295 0x296

What kernel version are you running?

[ticket]

After a while (running sensors every few minutes) the case fan rpm gets normal and stays that way (so far).

2.6.23.9

# isadump 0x295 0x296 WARNING! Running this program can cause system crashes, data loss and worse! I will probe address register 0x295 and data register 0x296. Continue? [Y/n] y

0 1 2 3 4 5 6 7 8 9 a b c d e f

00: 13 10 00 00 ff ff 00 37 ff 87 36 09 07 e8 e5 00 10: ff ff ff 33 d7 fe fc c2 02 02 00 ff ff ff ff ff 20: 3e 76 ce b4 bb c7 06 b7 be 26 24 1a 15 9f 9f 9f 30: ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 40: 7f 7f 7f 7f 7f 7f 5f 74 2d 40 90 22 ff ff ff ff 50: ff 1c 7f 7f 7f 50 04 04 90 04 0d 12 60 00 00 00 60: ff 14 00 27 90 03 ff ff 1b 1e 2d 20 b2 00 ff ff 70: ff 14 00 20 91 03 ff ff ff ff ff ff ff ff ff ff 80: 00 00 00 00 ff ff ff ff 00 00 ff ca 02 00 99 99 90: 7f 7f 7f 00 00 7f ff ff 7f 7f 7f 00 00 7f ff ff a0: 00 00 00 00 00 00 00 ff ff ff ff ff ff ff ff ff b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

[khali]

You did not answer my first question: what fan speed values does the BIOS show?

Also, does your BIOS offer an option to regulate the speed of the fans automatically? If so, is this option enabled?

Oh, and "normal" is not a fan speed. I want numbers.

[ticket]

Sorry, did not boot. It's Linux. But will remember to have a look.

Yes, according to the manual, the systemdoes offer fan-control. I will verify the settings in the BIOS when I reboot.

Normal is, as I wrote near the specced numbers. For the CPU-fan below 1000 rpm is OK. For the case fan 1500 rpm is the spec.

Now I see:

# sensors (...) CPU Fan: 852 RPM (min = 0 RPM) Case Fan: 7670 RPM (min = 0 RPM) (...)

Which is normal for CPU but abnormal for the case fan. Yesterday I had about the same rpms for CPU and case fan after a while, botth in the upper 800, low 900 range.

If the fancontrol is on, shouldn't the rpm reading still be consistent with the real rpm?

[khali]

Replying to ticket:

Now I see: # sensors (...) CPU Fan: 852 RPM (min = 0 RPM) Case Fan: 7670 RPM (min = 0 RPM) (...) Which is normal for CPU but abnormal for the case fan. Yesterday I had about the same rpms for CPU and case fan after a while, both in the upper 800, low 900 range.

This matches the values in the dump you attached: CPU fan at 907 RPM, system fan at 910 RPM.

If the fancontrol is on, shouldn't the rpm reading still be consistent with the real rpm?

Not necessarily, which is why I am asking. A common caveat of fan speed control with 3-wire fans is that the reliability of monitoring drops when you reach the low end of the speed range. The exact effects and limit value depend on several parameters (fan model, base frequency of the PWM signal, ability of the hardware monitoring chip to compensate for the signal weakness) but the general idea is that 3-wire fans can't be driven too slow or you lose the ability to monitor them.

If the BIOS was in fan control mode, try disabling it and see if it helps.

[ticket]

Found the fancontrol in the BIOS. One for CPU fan and another for System fan. Both enabled. Reading for System fan RPM was strange, values like: '<272' or ';440'. So also the BIOS was slightly confused. Disabled fan control for both.

[ticket]

Right after powerup, with the fancontrols disabled, I see: CPU Fan: 1113 RPM (min = 0 RPM) Case Fan: 1409 RPM (min = 0 RPM)

So fancontrol looks like it is a factor here.

[khali]

Indeed. Unfortunately there's not so much we can do then, this is a hardware limitation. You may try changing the base frequency of the PWM signal (/sys/class/hwmon/hwmon*/device/pwm2_freq) and see if it helps. But more likely you have to choose between reliable monitoring and fan speed control, you won't possibly have both at the same time. For the system fan that is, the CPU fan doesn't seem to suffer from this problem - maybe it's a 4-wire fan? Or maybe it just happens to deal better with the PWM signal. It really depends on the exact fan model.

[ticket]

The CPU fan is from a Zalman CNPS 7500-Cu+LED cooler. The case fan is specced as above. If this is behaviour within the limitation os the hard/software then you can close this item: sensors output is now with good rpms.