8.1 ALU Flashcards
How does a ripple carry full adder work (using full adders)
How does subtraction using two’s compliment and addition work
What is the diagram for a ripple-carry adder-subtractor
What is the ALU (and what functions does it have)
How to convert a number i into -i using two’s compliment
not i + 1
When does two’s compliment addition overflow occur
Final two carry bits unequal
What are some example ALU flag conditions
Why is repeated multiplication by addition a bad idea
Takes variable amount of time depending on data, eg: A + A vs A + A + A + A - twice as many loops.
How is binary multiplication done via shifts and adding
Same as denary 17 x 11 = (17 x 1 x 10^0) + (17 x 1 x 10^1)
What does a shift add multiplication circuit look like
How does wallace tree’s work for multiplication
3-group = full adder, 2 group = half adder. Reduces from O(n) layers to O(log(n) layers
CI at top, Res at bottom (for each layer). 3 inputs = FA
What does a wallace tree (final layer) circuit look like
What are fixed-function units
Unit with unique function eg: ALU, MUL, DIV etc.
