Overclocking computing cards

I have a compute rig with an ASpeed AST2400 GPU I use for the display and 3x GTX 980s for computing. I would like to overclock the nvidia gpus, which requires setting the coolbits option in xorg.conf.

So far I have been able to switch from modesetting to using xorg.conf using the following configuration (by setting dummy monitors for the GPUs):

# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig:  version 381.22  (buildmeister@swio-display-x86-rhel47-02)  Thu May  4 01:29:00 PDT 2017

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    Screen      1  "Screen1" RightOf "Screen0"
    Screen      2  "Screen2" RightOf "Screen1"
    Screen      3  "Screen3" RightOf "Screen2"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

Section "Files"
    FontPath        "/usr/share/fonts/default/Type1"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/input/mice"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor2"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "Monitor3"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "modesetting"
    VendorName     "ASpeed"
    BoardName      "AST2400"
    BusID          "PCI:7:0:0"
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 980"
    BusID          "PCI:2:0:0"
EndSection

Section "Device"
    Identifier     "Device2"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 980"
    BusID          "PCI:81:0:0"
EndSection

Section "Device"
    Identifier     "Device3"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce GTX 980"
    BusID          "PCI:82:0:0"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "Coolbits" "8"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen2"
    Device         "Device2"
    Monitor        "Monitor2"
    DefaultDepth    24
    Option         "Coolbits" "8"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen3"
    Device         "Device3"
    Monitor        "Monitor3"
    DefaultDepth    24
    Option         "Coolbits" "8"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

However I cannot enter nvidia-settings because it complains that I am not using the nvidia xorg driver. Everything else is configured properly (my CUDA programs work fine and nvidia-smi reports no problems).

So is it possible to overclock compute cards if I’m using the modesetting driver for my real display?

http://ubuntuforum-br.org/index.php/topic,117588.0.html