Fast Boot options - what does this mean for POST

reading the CCTK settings guide, I see there are three options for fastboot. Does anyone have any detailed info on what checks POST will perform for Thorough ?

I'm intersted in what POST does with memory at boot and whether selecting Thorough will write to all memory locations to enure all good.

--fastboot
Valid Argument thorough, minimal, automatic
Description Enables fast booting.
• thorough — Sets POST to perform complete hardware and
configuration testing.
• minimal — Sets POST to perform minimal hardware testing.
• automatic — Allows the BIOS to decide what level of POST test
is used.

Any info or links to official tech docs much appreciated.