Buffer Insertion Basics - Computer Engineering & Systems Group ...

Tapered Wire Sizing
Uniform Wire Sizing
Figure 6: Wire sizing with tapering and uniform wire sizing.
segment. These two cases are illustrated in Figure 6. It is shown in [25] that the benefit of wire
tapering versus uniform wire sizing is very limited when combined with buffer insertion. It is
theoretically proved [25] that the signal velocity from simultaneous buffering with wire tapering
is at most 1.0354 times of that from buffering and uniform wire sizing. In short, wire tapering
improves signal speed by at most 3.54% over uniform wire sizing.
4.6 Noise Constraints with Devgan Metric
The shrinking of minimum distance between adjacent wires has caused an increase in the coupling
capacitance of a net to its neighbors. A large coupling capacitance can cause a switching net
to induce significant noise onto a neighboring net, resulting in an incorrect functional response.
Therefore, noise avoidance techniques must become an integral part of the performance optimization
environment.
The amount of coupling capacitance from one net to another is proportional to the distance that
the two nets run parallel to each other. The coupling capacitance may cause an input signal on
the aggressor net to induce a noise pulse on the victim net. If the resulting noise is greater than
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