IO operations.
Do not work with immediates: only registers or memory locations.
http://stackoverflow.com/questions/14194798/is-there-a-specification-of-x86-i-o-port-assignment
http://superuser.com/questions/703695/difference-between-port-mapped-and-memory-mapped-access
in and out are used for port mapped IO.
In memory mapped IO, IO is done just like RAM IO.
TODO: see some circuit schematics.
TODO http://wiki.osdev.org/CMOS#Getting_Current_Date_and_Time_from_RTC says:
/* since the 0x80 bit of al is not set, NMI is active */
out 0x70, al
What does it mean?
man outb