Practice question · Multiple choice
A datapath is widened from 8 to 32 bits to handle larger values, and the maximum clock frequency drops. Why does a change about range affect speed?
Hints
- Ask what the longest path through a ripple-carry adder is, and how it scales with width.
- The clock period must exceed the critical path. What just happened to it?
Show the answer
B. Because a wider adder has a longer carry chain, so the clock must slow
Why
The carry must propagate across four times as many stages, so the critical path grows and the period must follow. Range and speed are coupled through the adder, which is why datapath width is an architectural decision rather than a detail, and why carry-lookahead exists to weaken the coupling.
Practise Integrated Digital-System Reasoning
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