How does the software in a motherboard change voltage?

[An00bis]

How does it do it? How is it possible?

 

[Soundmanred]

How does pushing button remote changing channels fast?
So fast!

 

[exdeath]

Writes to programmable IO registers in the chipset. The hardware itself is designed to control physical voltage based on values latched in the register.

You know when you go to device manager and everything on the computer has a I/O and memory address ranged assigned to it?