NCT6687D Kernel module

This kernel module permit to recognize the chipset Nuvoton NCT6687-R in lm-sensors package. This sensor is present on some B550 motherboard such as MSI or ASUS.

The implementation is minimalist and was done by reverse coding of Windows 10 source code from LibreHardwareMonitor

Installation

via package manager

.deb package

• Clone this repository

~$ git clone https://github.com/Fred78290/nct6687d
~$ cd nct6687d

• Build package

~$ make deb

• Install package

~$ dpkg -i ../nct6687d-dkms_*.deb

.rpm package (akmod)

• Clone this repository

~$ git clone https://github.com/Fred78290/nct6687d
~$ cd nct6687d

• Build & install package

~$ make akmod

Manual Install

Dependencies:

• Ubuntu/Debian: apt-get install build-essential linux-headers-$(uname -r) dkms dh-dkms
• Fedora/CentOS/RHEL: yum install make automake gcc gcc-c++ kernel-devel kernel-headers dkms
• ArchLinux: pacman -S make automake linux-firmware linux-headers dkms base-devel
• openSUSE: zypper in git make gcc dkms
  

Build with DKMS

~$ git clone https://github.com/Fred78290/nct6687d
~$ cd nct6687d
~$ make dkms/install

Manual build

~$ git clone (this-repo)
~$ cd nct6687d
~$ sudo make install

To remove a manual installation:

~$ sudo make uninstall

Sensors

By running the command sensors, you got this output

nct6687-isa-0a20
Adapter: ISA adapter
+12V:           12.17 V
+5V:             5.14 V
+3.3V:           3.38 V
CPU Soc:         1.11 V
CPU Vcore:       1.05 V
CPU 1P8:         1.84 V
CPU VDDP:        0.00 V
DRAM:            1.34 V
Chipset:       890.00 mV
CPU Fan:       1192 RPM
Pump Fan:      1538 RPM
System Fan #1:  922 RPM
System Fan #2:  953 RPM
System Fan #3: 1393 RPM
System Fan #4:    0 RPM
System Fan #5: 1007 RPM
System Fan #6:    0 RPM
CPU:            +59.0°C
System:         +34.0°C
VRM MOS:        +31.0°C
PCH:            +40.0°C
CPU Socket:     +33.0°C
PCIe x1:        +32.0°C
M2_1:            +0.0°C

Load(prob) Sensors on boot

To make it loaded after system boots

Just add nct6687 into /etc/modules

sudo sh -c 'echo "nct6687" >> /etc/modules'

Arch-Linux with systemd

See entry in the Arch Wiki

sudo sh -c 'echo "nct6687" >> /etc/modules-load.d/nct6687.conf'

Gnome sensors extensions

Tested

This module was tested on Ubuntu 20.04 with all kernel available on motherboard MAG-B550-TOMAHAWK running an AMD 3900X/AMD 5900X, and on RL8(RHEL8) MAG-B550M-MORTAR running an AMD 5700G

Other motherboard supported

• Many people have reported compatibility with MB having Intel H410M & H510M chipset from some manufacturer. See issue report.
  

CHANGELOG

• Add support for MSI B460M Bazooka having NCT6687 with another device ID
• Add support to use generic voltage input without multiplier, allows sensors custom conf
• Support giving fan control back to the firmware
  

VOLTAGE MANUAL CONFIGURATION

Some people report that voltage are wrong. The reason is with some motherboard, voltage sensors are not connected on the same nct6687 register.

As example the VCore sensor is connected on the 5th register for AMD but is connected on the 3rd register for INTEL.
Also the DIMM sensor is connected on the 4th register for AMD but connected to 5th register for INTEL.

To allow customize voltage configuration you must add manual=1 parameter passed to the module at load

sudo sh -c 'echo "nct6687 manual=1" >> /etc/modules'

And use a sensors conf like this /etc/sensors.d/B460M-7C83.conf

# Micro-Star International Co., Ltd.
# MAG B460M BAZOOKA (MS-7C83)

chip "nct6687-*"
    label in0         "+12V"
    label in1         "+5V"
    label in2         "VCore"
    label in3         "Voltage #1"
    label in4         "DIMM"
    label in5         "CPU I/O"
    label in6         "CPU SA"
    label in7         "Voltage #2"
    label in8         "+3.3V"
    label in9         "VTT"
    label in10        "VRef"
    label in11        "VSB"
    label in12        "AVSB"
    label in13        "VBat"

    ignore in3
    ignore in7
    ignore in9
    ignore in10
    ignore in13

    ignore temp6
    ignore temp7

    compute in0       (@ * 12), (@ / 12)
    compute in1       (@ * 5), (@ / 5)
    compute in4       (@ * 2), (@ / 2)

MODULE PARAMETERS

• force (bool) (default: false) Set to enable support for unknown vendors.

• manual (bool) (default: false) Set voltage input and voltage label configured with external sensors file. You can use custom labels and ignore inputs without setting this option if you can figure out their names (see which *_label contains builtin label).

• fan_config (default, msi_alt1) (default: default) Changes fan configuration for RPM & PWM registers for motherboards with alternative chip configurations.

  Motherboards which need this will show CPU/Pump RPMs but no data on System fans.

  msi_alt1 is automatically enabled for supported MSI motherboards. Manual configuration is only needed for unsupported boards.

• msi_fan_brute_force (bool) (default: false) [BETA] For MSI motherboards with msi_alt1 configuration: When enabled, writes PWM values to all 7 fan curve control points. This may help with fan control on some MSI boards where standard PWM writes don't take effect immediately. Only affects system fans controlled by the BIOS. Not the CPU fan or pump fan.

  Before entering manual control, the driver saves all 7 original curve points. The saved curve is restored when userspace writes automatic mode to pwmN_enable, when the driver is unloaded, or when the optional fan-control watchdog expires.

  This implementation is based on register mappings from LibreHardwareMonitor.

  Usage: modprobe nct6687 msi_fan_brute_force=1

  With this option enabled, the hwmon device exposes fan_control_watchdog. Writing a timeout from 1 to 300 seconds arms or refreshes a manual-control lease. If the lease expires, every channel changed since the last automatic-mode request is restored to its original curve and control mode. Writing 0 disarms the watchdog. A controlling daemon should refresh the lease independently of PWM value changes and disarm it only after returning all channels to automatic control. The lease is paused while the system is suspended and resumes with its remaining time after the device is active again.

  Note: This option requires blacklisting the nct6683 module to prevent it from loading instead of nct6687. See the Issues section for detailed instructions.

• fan_mask (uint) (default: all channels, 0xff) Bitmask of the fan/pwm channels to expose. Bit 0 controls fan1/pwm1, bit 1 controls fan2/pwm2, and so on up to bit 7 for fan8/pwm8. Both the tachometer and PWM attributes of a channel are covered by the same bit, since fanN_input and pwmN are the same physical header.

  Useful on boards with fewer than 8 headers, where the unused channels report a constant 0 RPM.

• temp_mask (uint) (default: all channels, 0x7f) Bitmask of the temperature channels to expose. Bit 0 controls temp1, up to bit 6 for temp7. Useful for hiding channels the board does not populate.

  Both masks accept decimal or 0x hex. Masked channels are not read from the EC at all, and channel numbering is never renumbered to fill gaps: masking off bit 1 leaves fan1 and fan3–fan8 with no fan2, so existing sensors.d and fancontrol configuration keeps referring to the same hardware.

  Examples:

  # fan1-fan6 and pwm1-pwm6 only, fan7/fan8/pwm7/pwm8 hidden
  # temp1-temp4 only, temp5/temp6/temp7 hidden
      options nct6687 fan_mask=0x3f temp_mask=0x0f
  

Supported MSI boards for ("msi_alt1" and "msi_fan_brute_force")

Board	DMI
PRO B840-P WIFI	MS-7E57
B840M GAMING PLUS WIFI6E	MS-7E77
B850 GAMING PLUS WIFI	MS-7E56
B850 GAMING PLUS WIFI6E	MS-7E80
B850M GAMING PLUS WIFI6E	MS-7E81
PRO B850-P WIFI	MS-7E56
PRO B850M-A WIFI	MS-7E66
PRO B850M-P WIFI	MS-7E71
MAG B850M MORTAR WIFI	MS-7E61
MAG B850 TOMAHAWK MAX WIFI	MS-7E62
MPG B850 EDGE TI WIFI	MS-7E62
MPG B850I EDGE TI WIFI	MS-7E79
B850MPOWER	MS-7E83
PRO B850-S WIFI6E	MS-7E80
X870 GAMING PLUS WIFI	MS-7E47
X870E GAMING PLUS WIFI	MS-7E70
MAG X870 TOMAHAWK WIFI	MS-7E51
PRO X870-P WIFI	MS-7E47
PRO X870E-P WIFI	MS-7E70
MAG X870E TOMAHAWK WIFI	MS-7E59
MAG X870E TOMAHAWK MAX WIFI PZ	MS-7E84
MPG X870E CARBON WIFI	MS-7E49
MPG X870E EDGE TI WIFI	MS-7E59
MEG X870E GODLIKE	MS-7E48
MEG Z890 ACE	MS-7E22
MEG Z890M ACE	MS-7E23
MPG Z890 CARBON WIFI	MS-7E17
MPG Z890M CARBON WIFI	MS-7E18
MPG Z890 EDGE TI WIFI	MS-7E19
MPG Z890I EDGE TI WIFI	MS-7E33
Z890 GAMING PLUS WIFI	MS-7E34
MAG Z890 TOMAHAWK WIFI	MS-7E32
PRO Z890-A WIFI	MS-7E32
PRO Z890-P WIFI	MS-7E34
PRO Z890-S WIFI	MS-7E54

CONFIGURATION VIA SYSFS

In order to be able to use this interface you need to know the path as which it's published. The path isn't fixed and depends on the order in which chips are registered by the kernel. One way to find it is by device class (hwmon) via a simple command like this:

for d in /sys/class/hwmon/*; do echo "$d: $(cat "$d/name")"; done | grep nct6687

Possible output:

/sys/class/hwmon/hwmon5: nct6687

This means that your base path for examples below is /sys/class/hwmon/hwmon5 (note that adding/removing hardware can change the path, drop grep from the command above to see all sensors and their relative ordering).

Another way to look it up is by a device (class path actually just points to device path) like in:

cd /sys/devices/platform/nct6687.*/hwmon/hwmon*

The first asterisk will be expanded to an address (2592 which is 0xa20 that you can see in sensors output) and the second one to a number like 5 from above.

pwm[1-8]

Gets/sets PWM duty cycle or DC value that defines fan speed. Which unit is used depends on what was configured by firmware.

Accepted values: 0-255 (slowest to full speed).

Writing to this file changes fan control to manual mode.

Example:

# slow down a fan as much as possible (will stop it if the fan supports zero RPM mode)
echo 0 > pwm6
# fix a fan at around half its speed (actual behaviour depends on the fan)
echo 128 > pwm6
# full speed
echo 255 > pwm6

pwm[1-8]_enable

Gets/sets the fan control mode.

Accepted values:

• 1 - manual speed management through pwm[1-8]
• 2 - automatic control using the profile configured by firmware

The legacy value 99 is still accepted when written for compatibility, but reading pwm[1-8]_enable always reports the standard hwmon value 1 or 2.

Example:

# fix a fan at current speed (`echo pwm6` will be constant from now on)
echo 1 > pwm6_enable
# switch back to automatic control set up by firmware (`echo pwm6` is again dynamic after this)
echo 2 > pwm6_enable
# switch to ~25% of max speed
echo 64 > pwm6
# automatic
echo 2 > pwm6_enable
# back to ~25% (it seems to be remembered)
echo 1 > pwm6_enable

VERIFIED

1. Fan speed control

• Changing fan speed was tested successfully by users, see in reported issues.

Issues

Loading fails during startup

dmesg / journalctl shows

kernel: nct6687: EC base I/O port unconfigured
systemd-modules-load[339]: Failed to insert module 'nct6687': No such device

• add softdep nct6687 pre: i2c_i801 to e.g. /etc/modprobe.d/sensors.conf.

Loading msi_fan_brute_force parameter fails

• Symptom: No RPM value is displayed for some fans in the sensor data; or the following behavior is observed: the fan stops at 60%

• Solution steps:

  1. Prevent the wrong driver from loading:

     echo "blacklist nct6683" | sudo tee /etc/modprobe.d/nct6683_blacklist.conf
     

  2. Set module option to enable brute-force fan curve writes for MSI boards:

     echo "options nct6687 msi_fan_brute_force=1" | sudo tee /etc/modprobe.d/nct6687_msi.conf
     

  3. Ensure the nct6687 module is loaded at boot:

     echo "nct6687" | sudo tee /etc/modules-load.d/nct6687.conf
     

  4. Reboot and verify the module loads correctly.

• After installation: Check /etc/conf.d/lm-sensors.conf (or your distro's equivalent) that HWMON_MODULES not includes nct6683 (e.g., HWMON_MODULES="coretemp nct6683 ...") to ensure the correct driver is loaded at boot.

Only CPU & Pump show RPM values

On MSI motherboards, msi_alt1 configuration is automatically detected and enabled. You can verify this in dmesg after loading the module:

nct6687 nct6687.2592: Detected MSI board; using alternative fan configuration (msi_alt1)
nct6687 nct6687.2592: active fan config=msi_alt1, SYS_FAN reg_rpm=0x015E/0x015C/0x015A

The second line is always printed and shows the EC offsets the driver reads for SYS_FAN #1/#2/#3. Use it to confirm the right mapping is active.

If you have a non-MSI motherboard with this issue, try using module parameter fan_config=msi_alt1 manually.

Warning — do NOT force fan_config=msi_alt1 on non-listed MSI boards. Only the NCT6687DR-equipped MSI families (B840/B850/X870/X870E/Z890) are compatible with msi_alt1. Earlier MSI series with the plain NCT6687D chip — including B650/B660/X670/Z690/Z790 — use the default register mapping and are auto-detected correctly without any module parameter.

If you previously set options nct6687 fan_config=msi_alt1 in /etc/modprobe.d/ on one of those boards as a troubleshooting attempt, remove it: forcing msi_alt1 makes the driver read EC offsets 0x154-0x15E which are zero on non-DR variants, causing all SYS_FAN to report 0 RPM while CPU_FAN keeps working. The active fan config=... dmesg line above will reveal a stale forced setting at a glance.

Reference: issue #167 (MSI MPG B650 CARBON WIFI, MS-7D74).