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undervoltage Tools for MacOS
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VoltageShift.xcodeproj Updated for setting turbo boost and power limited May 26, 2019
VoltageShiftAnVMSR Updated for setting turbo boost and power limited May 26, 2019
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LICENSE Create LICENSE Jun 18, 2017 Update README May 26, 2019


Undervoltage Tools for MacOS (Haswell and Broadwell)
All source code protected by The GNU General Public License V 3.0
MSR Kext Driver modified from AnVMSR by Andy Vandijck Copyright (C) 2013 AnV Software


You can download this software´s binary from our site - VoltageShift


Xcode is required. Build the kernel extension (kext):

 xcodebuild  -target VoltageShift.kext

change the owner to root:wheel for the kext
sudo chown -R root:wheel build/Release/VoltageShift.kext

Build the command line tool:

 xcodebuild  -target voltageshift


New Versions 1.2:

  1. Updated for support up to 8 core CPU
  2. Updated setting of turbo boost
  3. Updated setting of power limited
  4. Additional power limited and turbo boost status showed on -info
  5. info showed as OC_Locked mean Apple locked the BIOS and not aviliable change of voltage

This program is a command tool that supports Haswell and above CPUs for undervoltage.

It uses 'Intel Overclock Mailbox' for controling the voltage offset, Your system may be locked of the "OC Mailbox" and not be available for undervoltage.

Undervoltage can reduce heat and sustain Turbo boost longer, provide longer battery performance, although if done too much(mV) it may cause an unstable system.

This program does not provide a GUI interface because it loads the MSR driver only when apply, amend or read is done, after that the MSR driver will load and unload immediately for more security and lowest resource usage, after you test the settings well, you can use our tools to build the launchd for autorun on startup and maintaining the settings, please read below for more details.

This program supports macOS 10.12 or above, however you need to switch off the SIP for unsigned kext in Recovery mode:

Push Cmd+R when booting to Recovery mode, select Terminal at toolbar and enter:

csrutil enable --without kext

After reboot, ensure the kext and the command tool files are in the same directory.

You can view your current voltage offset,CPU freqency,power and temperture settings with the following command:

./voltageshift info

You can continue to monitor the CPU frequency, power and temperture by using:

./voltageshift mon

Six types of voltage offset are disponible to change, however we only suggest undervolting the CPU and GPU only.

./voltageshift offset <CPU> <GPU> <CPUCache> <SystemAgency> <Analogy I/O> <Digital I/O>

for example reduced CPU -50mv and GPU -50mv

./voltageshift offset -50 -50

If you set it too low the system will freeze, please turn OFF completely and turn ON computer to reset back the undervolt to 0mV.

After you test throughfuly the settings and are comfortable with System stability, you can apply the launchd: (require sudo root)

sudo ./voltageshift buildlaunchd  <CPU> <GPU> <CPUCache> <SystemAgency> <Analogy I/O> <Digital I/O> <Update Mins>

The is the update interval of the tool to check and change, the Default value is 160min, Hibernate (suspend to Disk) will reset the voltage setting, as sleep (suspend to memory) will not change the sleep value, it will scheduled check the setting in peroid, and amend if need.

 0 is for applying the setting at bootup only.

for example:

sudo ./voltageshift buildlaunchd  -50 -50 0 0 0 0 60

set system auto apply CPU -50mv and GPU -50mv every boot and every 60 minutes.

You can remove the launchd with the following command:

 ./voltageshift removelaunchd

We also suggest to run first removelaunchd and them buildlaunchd if you want to change the launchd settings.


Use '--damage offset ...' if you want settings lower than 250mv or Overvoltage (>0v).

Manually change the launchd (com.sicreative.VoltageShift.plist under /Library/LaunchDaemons) by adding new ProgramArguments '--damage' between '/Library/Application Support/VoltageShift/voltageshift' and 'offsetdaemons'

To read the MSR

  ./voltageshift read <HEX_MSR>

To set the MSR

 ./voltageshift write <HEX_MSR> <HEX_VALUE>

To set the Power Limted of PL1 (Long Term) and PL2 (Short Term)

./voltageshift power <PL1> <PL2>

To set Turbo Enabled (0-no turbo 1-turbo):

./voltageshift turbo <0/1>
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