Area vs. Speed

• Two generally mutually exclusive goals are minimum delay and minimum area

• An example using Synopsys Inc.’s tools produces the following results:

  • design optimized for speed resulted in 197 gates with a critical path of 6.6ns
  • design optimized for area resulted in 115 gates with a critical path of 10.9ns
  • design for best characteristics for both speed and area resulted in 141 gates with a critical path of 8.2ns

Propagation Delay

Smallest

Fastest

Starting Point

After Area Opt.

After Timing Opt

Area

[de Geus89]

Previous slide

Next slide

Back to first slide

View graphic version

Example from [de Geus89], p. 28.

Note that third option lies between first two in both gate count and speed.

Mentor Graphics’ Autologic recommends optimizing for area first, then delay, then area again, etc.