Spatial entropy: A unified attribute to model dynamic communication in VLSI circuits
This dissertation addresses the problem of capturing the dynamic communication in VLSI circuits. There are several CAD problems where attributes that combine behavior and structure are needed, or when function behavior is too complex and is best captured through some attribute in the implementation....
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| Format: | Dissertation |
| Language: | English |
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ProQuest Dissertations & Theses
01-01-1992
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| Online Access: | Get full text |
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| Summary: | This dissertation addresses the problem of capturing the dynamic communication in VLSI circuits. There are several CAD problems where attributes that combine behavior and structure are needed, or when function behavior is too complex and is best captured through some attribute in the implementation. Examples include, timing analysis, logic synthesis, dynamic power estimation, and variable ordering for binary decision diagrams (BDDs). In such a situation, using static attributes computed from the structure of the implementation is not always helpful. Firstly, they do not provide sufficient usage information, and secondly they tend to exhibit variances with implementations which is not desirable while capturing function behavior. The contribution of this research is a new circuit attribute called spatial entropy. It models the dynamic communication effort in the circuit by unifying the static structure and the dynamic data usage. Quantitatively, spatial entropy measures the switching energy in a physical (CMOS) implementation. A minimum spatial entropy implementation is a minimum energy implementation. For the purposes of this dissertation we restrict our scope to combinational circuits. We propose a simple procedure to estimate spatial entropy in a gate level circuit. It is characterized in extensive detail and we describe why it is difficult to compute spatial entropy accurately. We show how it can also be defined at other levels of abstraction. We illustrate applications of spatial entropy in BDD variable ordering, a problem that has traditionally relied on static attribute based solutions. We also show empirically that spatial entropy can track function behavior through implementations, by using it to measure gate-count complexity in boolean functions. |
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| ISBN: | 9798208097908 |