ECE 09241 Lecture Notes - Longest Path Problem, Critical Path Method, Register File
12 May 2022
School
Department
Course
Professor
Document Summary
Intro to digital systems course notes: lecture 12. A particular desired behavior, like adding two 4-bit numbers, may have alternative circuit implementations. A tradeoff is a design decision that improves one implementation metric while worsening another. An implementation metric is a measurement of an implementation"s goodness. A common circuit metric is a circuit"s size, with smaller size being better. Another is circuit delay, with less delay being better. Unfortunately, decreasing size usually increases delay, representing a tradeoff. In contrast to a tradeoff, a design decision that improves some metric(s) without worsening any others is called an optimization. Multiple approaches exist for determining circuit size. One approach estimates transistors, assuming every gate input requires 2 transistors, and ignoring inverters for simplicity. A 2-input gate requires 2 inputs 2 trans/input = 4 transistors. A 3-input gate requires 3 2 = 6 transistors. Wires also contribute to size, but ignoring wires as above is a common approximation.
