the human brain is not a computer for the sole reason that a human has a finite life time.

The programs that a human brain can execute are strictly limited to the subset of all programs that can be computed in (C steps per year)*(100 years).

A real computer such as the one you are looking at right now is more powerful than a human because it can run all programs that halt within (U steps per year where U>C)*(W steps per year where W>100)

Both humans and real computers are also limited by the programs that they can find and execute

simple as