A typical use of a MUX in a processor control path
Consider the following sequence of instructions:
0x7F800 add $16, $18, $15 # reg16 ? reg18 + reg15
0x7F804 beq $8, $0, target # if reg16 == 0 goto target
0x7F808 sub $17, $17 $15 # reg17 ? reg17 - reg15