As some of you might remember - I have implemented a Timed-Sequence Multiply
with Nibble Skip (4 Bits). Where one 4 x 4 Multiply, Add and Accumulate requires 22 NS. Worst case is 8 x 22 = 176 NS. Best case = 22 NS. I get around the variable timing by Enabling the Multiply Interrupt and execute a HALT instruction.
I also use an Interrupt to recognize a Divide termination. The divide is variable because I skip One's and Zero strings.