Both CeltIC and PrimeTime-SI provide a post-route analysis of crosstalk-induced delay and noise, although PrimeTime-SI has lagged behind CeltIC in the availability of noise libraries. A posting in ESNUG last September stated that PrimeTime-SI was not handling "functional" noise issues, such as glitches, because it lacked the needed library characterization.

An October 2003 ESNUG posting from an engineer at Broadcom provided a lengthy benchmark, concluding that CeltIC had better bounded accuracy than PrimeTime-SI for crosstalk-induced delays. The engineer said his company intends to use CeltIC for all crosstalk, glitch and delta delay analysis, even though CeltIC is "quite pessimistic" in its most accurate mode.

John Cooley's Design Automation Conference "trip report" included a number of postings singing the praises of CeltIC. While there were a few complaints, users lauded its speed, accuracy and ability to minimize false positives. Several specifically said that CeltIC is a better tool than PrimeTime-SI.

Jay McDougal, microprocessor design methodology manager at Agilent, called PrimeTime-SI "overly pessimistic" compared with CeltIC. But he had to use PrimeTime-SI with his 90-nm chip design because it was Agere's official sign-off tool.

'Real waveforms'
Vinod Kariat, R&D group director for timing and signal-integrity at Cadence, said that CeltIC is more accurate and less pessimistic than PrimeTime-SI. He said it can handle nonlinearity very well. "The fundamental difference is that we use real waveforms and circuit simulation, while PrimeTime-SI uses table lookups," he said.

So what does Synopsys have to say for itself? Rajiv Maheshwary, senior director of marketing for Synopsys' implementation group, acknowledged that CeltIC had a head start in crosstalk noise analysis, which requires special libraries. But noise libraries are now becoming available for PrimeTime-SI, he said, and customers are "aggressively adopting" them.

Yes, CeltIC is simulation-based, but PrimeTime-SI is three to six times faster and easier to use, Maheshwary said. He insisted that PrimeTime-SI's delay accuracy is about the same as CeltIC and that its noise accuracy is also as good, typically within 2 to 3 percent of Spice. If used properly, he said, PrimeTime-SI is no more pessimistic than CeltIC.