
Switched Carry-Ripple (Manchester) Adder
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2.3
Reducing the Adder Delay
The delay of the carry-ripple adder can be reduced by the following four ap-
proaches:
1. Reducing the carry delay t~. This is achieved in the switched carry-ripple
(Manchester) adder.
2. Changing the linear factor n to a "smaller" factor (such as n/k or log n).
This is achieved by the carry-skip adder, the carry-lookahead adder, the
prefix adder, the carry-select adder, and the conditional-sum adder.
3. Including a completion signal so that the addition time corresponds to the
actual addition and not to the worst case.
4. Changing the number representation ...