Well, a new motherboard: the MSI Z77A-GD65 (internal code name MS-7751 v2.1). If you’re interested why I chose it, ask. If not, let’s get on with a favourite pet peeve of mine: monitoring with lm-sensors.

One of the reasons I chose the MSI Z77A-GD65 was the fact it has 5 fan headers: 1 for the CPU fan and 4 for case fans. Digging into docs, turns out 2 fan headers can be controlled through PWM (headers have 2 pins for power, 1 pin for reading the fan speed and 1 pin for setting the fan speed) while the other two fan headers are 3 pin (no fan speed setting, just monitoring). Oh well I said, good enough. Unfortunately, it seems MSI were lying a bit: just the 2 PWM fan headers have the speed monitoring pin connected, while the other two are just power supply headers and provide no fan speed monitoring (even if they have 3 pins).

The MSI Z77A-GD65 uses a F71889A IO chip from Fintek. It seems pretty capable, but it’s not fully used inside the Z77A-GD65. Support in lm-sensors for the F71889A was added since ~June 2011 and running the classical sensors-detect does a good job in finding and configuring the chip. Reading the F71889A data sheet, we can see why only 3 fans are monitored and controlled by the board: it’s a limitation of the monitoring chip. Oh well.

Here’s the relevant section from /etc/sensors3.conf:

chip "f71808e-*" "f71808a-*" "f71862fg-*" "f71869-*" "f71869a-*" "f71882fg-*" \
     "f71889fg-*" "f71889ed-*" "f71889a-*"

    label in0 "+3.3V"
    label in7 "3VSB"
    label in8 "Vbat"

#    compute in0  @*2, @/2
#    compute in7  @*2, @/2
#    compute in8  @*2, @/2

    label temp1 "Temp1"
    label temp3 "Temp3"
    ignore temp2
    label fan1 "CPU FAN"
    label fan2 "SYSFAN1"
    label fan3 "SYSFAN2"

What’s changed beside the stock configuration ? the compute modifications don’t seem to be required, so they’re commented out. The two temperature inputs are properly labeled (Temp1 and Temp3) while Temp2 is not connected – so it’s set to be ignored. Add the 3 fan labels and that’s pretty much it.

Output from sensors shows the ACPI thermal zone temperatures, the CPU core temperatures and the inputs from the F71889A chip:

Adapter: Virtual device
temp1:        +27.8 C  (crit = +106.0 C)
temp2:        +29.8 C  (crit = +106.0 C)

Adapter: ISA adapter
Physical id 0:  +34.0 C  (high = +85.0 C, crit = +105.0 C)
Core 0:         +34.0 C  (high = +85.0 C, crit = +105.0 C)
Core 1:         +28.0 C  (high = +85.0 C, crit = +105.0 C)
Core 2:         +23.0 C  (high = +85.0 C, crit = +105.0 C)
Core 3:         +33.0 C  (high = +85.0 C, crit = +105.0 C)

Adapter: ISA adapter
+3.3V:        +3.34 V  
in1:          +0.85 V  (max =  +2.04 V)
in2:          +0.01 V  
in3:          +0.94 V  
in4:          +1.10 V  
in5:          +0.74 V  
in6:          +1.05 V  
3VSB:         +3.34 V  
Vbat:         +3.38 V  
CPU FAN:      572 RPM
SYSFAN1:     1347 RPM
SYSFAN2:     1338 RPM
Temp1:        +32.0 C  (high = +255.0 C, hyst = +251.0 C)  ALARM (CRIT)
                       (crit = +255.0 C, hyst = +251.0 C)  sensor = transistor
Temp3:        +28.0 C  (high = +255.0 C, hyst = +253.0 C)  ALARM (CRIT)
                       (crit = +255.0 C, hyst = +253.0 C)  sensor = transistor    

Unfortunately, the two temperature limits are not software configured through lm-sensors, but directly reported from the F71889A chip (it permanently raises the alarm flag which means it’s not properly connected/configured). That’s it. If you manage to improve it, do drop a comment below.

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