is that the default setting after system powerup, or did you modify it ?
Just wondering, since the NCT6775 is usually configured for automatic fan
control (which, in my experience, works pretty well).
Anyway, the fans are all in pwm mode, so I think Jean is right and the fan just
doesn't get slower than 1000 rpm. Which may explain why one of the fans in my
system runs at 1000 rpm, even though it turns out that its pwm value is lower
than the other fan's pwm value.
I modified it to manual and changed the PWM divisor to see what speeds I could get. I agree that Jean's diagnosis makes sense.
It isn't that the automatic fan control didn't work well, in fact it never gave me problems. This might sound weird, but I actually need the fan speed lower to reach a specific (lower) TDP for experimental work.
After playing around with the heatsink and fan settings, the TDP is currently pretty close to what I ideally want, to within about 5W. I was hoping to shave off 5W more by reducing fan speed further.
For comparison, here is the output for pwm1 on my system with NCT6775.
/sys/class/hwmon/hwmon1/device/pwm1:64
/sys/class/hwmon/hwmon1/device/pwm1_auto_point1_pwm:50
/sys/class/hwmon/hwmon1/device/pwm1_auto_point1_temp:5000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point1_temp_hyst:3000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point2_pwm:77
/sys/class/hwmon/hwmon1/device/pwm1_auto_point2_temp:89000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point2_temp_hyst:87000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point3_pwm:77
/sys/class/hwmon/hwmon1/device/pwm1_auto_point3_temp:89000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point3_temp_hyst:87000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point4_pwm:123
/sys/class/hwmon/hwmon1/device/pwm1_auto_point4_temp:98000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point4_temp_hyst:96000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point5_pwm:166
/sys/class/hwmon/hwmon1/device/pwm1_auto_point5_temp:101000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point5_temp_hyst:99000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point6_pwm:255
/sys/class/hwmon/hwmon1/device/pwm1_auto_point6_temp:104000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point6_temp_hyst:102000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point7_pwm:255
/sys/class/hwmon/hwmon1/device/pwm1_auto_point7_temp:114000
/sys/class/hwmon/hwmon1/device/pwm1_auto_point7_temp_hyst:114000
/sys/class/hwmon/hwmon1/device/pwm1_enable:5
/sys/class/hwmon/hwmon1/device/pwm1_max_output:255
/sys/class/hwmon/hwmon1/device/pwm1_mode:1
/sys/class/hwmon/hwmon1/device/pwm1_start_output:1
/sys/class/hwmon/hwmon1/device/pwm1_step_down_time:100
/sys/class/hwmon/hwmon1/device/pwm1_step_enable:1
/sys/class/hwmon/hwmon1/device/pwm1_step_output:1
/sys/class/hwmon/hwmon1/device/pwm1_step_up_time:200
/sys/class/hwmon/hwmon1/device/pwm1_stop_output:1
/sys/class/hwmon/hwmon1/device/pwm1_stop_output_enable:0
/sys/class/hwmon/hwmon1/device/pwm1_stop_time:6000
/sys/class/hwmon/hwmon1/device/pwm1_target:1000
/sys/class/hwmon/hwmon1/device/pwm1_temp_sel:8
/sys/class/hwmon/hwmon1/device/pwm1_weight_duty_step:36
/sys/class/hwmon/hwmon1/device/pwm1_weight_enable:1
/sys/class/hwmon/hwmon1/device/pwm1_weight_temp_sel:1
/sys/class/hwmon/hwmon1/device/pwm1_weight_temp_step:2000
/sys/class/hwmon/hwmon1/device/pwm1_weight_temp_step_base:70000
/sys/class/hwmon/hwmon1/device/pwm1_weight_temp_step_tol:1000
This is with the new driver for the NCT677X chips, which supports automatic
fan control. Might be worthwhile to give it a try if you want to use
automatic fan control.
Thanks. I'm trying to retain control of the thermals for a study. Actually, could you provide some more info on how the automatic control works? In specific, does it try to keep *average* temperature under control by modulating fan speed, or can I get it to keep a constant fan speed so that temperature doesn't fluctuate (i.e. a plot of temperature v/s time would be monotonic under constant input power)? That might work for me too.
Otherwise, as Jean said, I will have to look at replacing the fan and/or changing input voltage.
thanks,
-arun
Thanks,
Guenter