Linux-PHC is a project to enable Linux users to undervolt their CPUs. Just like NHC or Rightmark RMClock for
Windows users can lower the voltages of their CPUs to expand battery time and reduce the CPUs temperature.

This is possible because we utilize the production tolerance of a CPU. CPUs have different production qualities so the vendor defines voltages every CPU -even those with low quality- will work with.
If your CPU is of higher quality you can easily run it with lower voltages without getting unstable.