Why are the fast integer types faster than the other integer types?

Question

In ISO/IEC 9899:2018 (C18), it is stated under 7.20.1.3:

7.20.1.3 Fastest minimum-width integer types

1 Each of the following types design

Answer 1

The fast types are not faster than all other integer types -- they are in fact identical to some "normal" integer type (they're just an alias for that type) -- whichever type happens to be the fastest for holding a value of at least that many bits.

It just platform-dependent which integer type each fast type is an alias for.