Dell Precision 7530 - Undervolting using EFI Variables

Discussion in 'Dell Latitude, Vostro, and Precision' started by harmandeep, Nov 26, 2021.

  1. harmandeep

    harmandeep Notebook Enthusiast

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    Hi,

    I have two Dell mobile workstations - Precision 7530 and 7540. I am looking for assistance with Undervolting using EFI variables.
    After updating System Firmware, undervolting was disabled which was then fixed changing few EFI variables.


    Disable 'CFG Lock': setup_var_3 0x5BD 0x0
    Disable 'Overclocking Lock': setup_var_3 0x659 0x0
    Enable 'OverClocking Feature': setup_var_3 0x725 0x1



    Since Hyper-V is now blocking access to MSR registers, so I cannot use Throttlestop or any such programs to make necessary modifications as MSR registers are protected.
    Hence I want to make TESTED Undervolting changes at System firmware level.

    On my Dell Preicison 7530 without Hyper-V, below undervolt settings via throttlstop are stable enough.
    upload_2021-11-26_19-57-19.png

    CPU Core = -0.1455mv
    CPU Uncore / Cache = -0.1455mv [please correct me if Uncore is not CPU cache]
    iGPU GT Core = -0.0352mv
    iGPU GT Uncore/unslice = -0.0352mv
    System Agent = -0.0303mv


    I want to set these undervolt changes using EFI variables. I have tried the below settinngs but somehow changes are not effective. I have tried many times but to no avail.

    setup_var_3 0x72D 0x1 (core voltage offset prefix to -)
    setup_var_3 0x72B 0x91 (core voltage offset to -145)

    setup_var_3 0x9D2 0x1 (Uncore voltage offset prefix to -)
    setup_var_3 0x9D0 0x91 (Uncore voltage offset to -145)

    setup_var_3 0x9DA 0x1 (GT voltage offset prefix to -)
    setup_var_3 0x9D8 0x23 (GT voltage offset to -35)

    setup_var_3 0x9E1 0x1 (GTU voltage offset prefix to -)
    setup_var_3 0x9E3 0x23 (GTU voltage offset to -35)



    Can some one please guide me.
    Dell Precision 7530 variables list is attached.

    BIOS region dump is available here which can be opened in AMIBCP.

    Regards
    Harmandeep
     

    Attached Files:

  2. harmandeep

    harmandeep Notebook Enthusiast

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  3. harmandeep

    harmandeep Notebook Enthusiast

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  4. harmandeep

    harmandeep Notebook Enthusiast

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    I found a workaround which is okay for my use case. My dell workstations run 24x7.
    Workaround:

    1) Boot without Hyper-V
    [​IMG]

    2) Make changes and select options for persistent settings. Persistent settings makes sure that MSR registers settings aren't cleared upon reboot.

    upload_2021-11-27_21-43-12.png

    3) Upon reboot to OS with Hyper-V, changes will be effective. You cannot see Voltage offsets/MSR registers values but you can observe changes via stress testing and observing temps/fan curve.
    With warm startup, MSR registers are cleared and the workaround procedure has to repeated. This task can be automated with Powershell. Haven't tested s3 sleep but I believe MSR registers will be cleared upon wake.

    In my case, 8750h Cinebench score improved by 20%, from 1000 to appox 1200 while temps dropped by 20-25 degrees.
     
    Last edited: Nov 27, 2021
    Ionising_Radiation likes this.
  5. Ionising_Radiation

    Ionising_Radiation ?v = ve*ln(m0/m1)

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    Great post for those on the 7530, without working in the dark and attempting to roll back the firmware.
     
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