>> Instead of multiplying by 7, you add 8 times the number and subtract the number, ending up with 7 times the number. You might think this requires two steps, but the trick is to multiply by one more in the digit to the left, so you get the factor of 8 without an additional step.
Does this mean there's an "adder" to add 1 to the "next digit" prior to feeding the digits to the main part of the multiplier? That itself seem like it'd be similar to the carry lookahead circuit. Also thinking about when that needs to be done:
7 = 8-1
6 = 8-2
5 = 8-3
4 = 8-4 <- he didn't say they do this, but it would mean the MSB of the 3-bit value could be used to determine if we need to add 1 to the next digit, saving a couple gates.
Does this mean there's an "adder" to add 1 to the "next digit" prior to feeding the digits to the main part of the multiplier? That itself seem like it'd be similar to the carry lookahead circuit. Also thinking about when that needs to be done:
7 = 8-1
6 = 8-2
5 = 8-3
4 = 8-4 <- he didn't say they do this, but it would mean the MSB of the 3-bit value could be used to determine if we need to add 1 to the next digit, saving a couple gates.