Before you make the chip, you need to understand how to do it on paper. It looks like normal multiplication but with only 1s and 0s.
25
* 7
______
7*5= 35
7*2 = 140 (add a zero)
35+140 = 175
__________________________________________________________
Binary multiplication.
0111
* 0011
____________
1*0111 = 0111
1*0111=01110 (add zero)
0*0111=0
0*0111=0
____________________
0111+1110=10101
You can further simplify this by seeing that all of the partial products are the first number with zeros added. You can think of it like this.
0111
0011
_______
0000111 * 1
0001110 * 1
0011100 * 0
0111000 * 0
+
As you can see, we laid out the second number to the side. If it was 1, then would add the shifted first number other wise we would not..
You can make this in gates by first getting 3, 8-bit adders and hook up the fist two outputs to the seconds one's input (Not the carry). this lets your add 4 numbers together. Your then add 16 and gates, four for each input. Attach the first number to all of the sets of four and gates. For the other input of the and gate, use only one bit of the second number for each set of and gates. Attach the gate that is connected to the second numbers smallest place, to the bottom of the first adder input. Then attach the gates with the second lowers input to the other input of the adder, but shift it one up. Con tine this until you have done all four. The end result looks like this:
