Example undervolt script for i7-8550U processor, Dell XPS 13 9360

undervolt-sleep.service

[Unit]
Description=Undervolting preset resume after sleep
After=suspend.target

[Service]
Type=oneshot
ExecStart=/bin/bash /opt/undervolt_check_and_apply.sh

[Install]
WantedBy=suspend.target

undervolt-start.service

[Unit]
Description=Undervolting preset resume after startup

[Service]
Type=oneshot
ExecStart=/bin/bash /opt/undervolt_check_and_apply.sh

[Install]
WantedBy=multi-user.target

undervolt_check_and_apply.sh

#!/bin/bash

# Check for core offset
wrmsr 0x150 0x8000001000000000
if [ $(rdmsr 0x150) == "0" ]; then
        wrmsr 0x150 0x80000011f2800000 # -0.1055V
        echo "Core offset set!"
else
        echo "Core offset is already set!"
fi

# Check for GPU offset
wrmsr 0x150 0x8000011000000000
if [ $(rdmsr 0x150) == "0" ]; then
        wrmsr 0x150 0x80000111f5c00000 # -0.0801V
        echo "GPU offset set!"
else
        echo "GPU offset is already set!"
fi

# Check for cache offset
wrmsr 0x150 0x8000021000000000
if [ $(rdmsr 0x150) == "0" ]; then
        wrmsr 0x150 0x80000211f2800000 # -0.1055V
        echo "Cache offset set!"
else
        echo "Cache offset is already set!"
fi