Answer from cs61c-ac (U alias Vitoria Lok 16597715) for Question 4
An I/O scheme in iwhich portions of address spaces are assigned to I/O devices and reads and writes to those addresses are interpreted as commands to the I/O device.
addi t1, $0, 0x0000ffff
Loop: lw $t0, 0($t1)
      sw $t0, 4($t1)
      j Loop