Comment by pantantrant

Example:

ax is a 2 bit register initialized to 0.

100: add 1 ax

101: jmp 100

ax is 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3

0 is compared to 1, 1 is compared to 3, 3 is compared to 2, 2 is is compared to 2, wait, that's an infinite loop...