For performance optimization tasks such as floorplanning, placement, buffer
insertion, wire sizing, and global routing, the Elmore resistance-capacita
nce (RC? delay metric remains popular due to its simple closed form express
ion, fast computation speed, and fidelity with respect to simulation. More
accurate delay computation methods are typically central processing unit in
tensive and/or difficult to implement. To bridge this gap between accuracy
and efficiency/simplicity, we propose two new RC delay metrics called delay
via two moments (D2M) and effective capacitance metric (ECM), which are vi
rtually as simple and fast as the Elmore metric, but more accurate. D2M use
s two moments of the impulse response in a simple formula that has high acc
uracy at the far end of RC lines. ECM captures resistive shielding effects
by modeling the downstream capacitance by an "effective capacitance." In co
ntrast, the Elmore metric models this as a lumped capacitance, thereby igno
ring resistive shielding. Although not as accurate as D2M, ECM yields consi
stent performance and may be well-suited to optimization due to its Elmore-
like recursive construction.