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.

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 attached which can be opened in AMIBCP.

Regards
Harmandeep

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

1) Boot without Hyper-V


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


3) Upon reboot to OS with Hyper-V, changes will be effective. You cannot see Voltage offsets/MSR registers values with Hyper-V active but you can verify Undervolt changes via synthetic stress testing and monitoring voltage/fan curve/emissions.

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.

Zitat von harmandeep im Beitrag #1

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I have tried the below settinngs but somehow changes are not effective.

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yes,
Enable 'OverClocking Feature': setup_var_3 0x725 0x1

Zitat von harmandeep im Beitrag #4

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yes

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