SANTA CRUZ, Calif. One holdup with statistical timing analysis has been generating the models that support it, but that situation may ease this week. Startup Altos Design Automation Inc. will roll out Variety, which it claims is a fast statistical library characterization tool, and is making it available to the Silicon Integration Initiative (Si2) for use in a pivotal library standards effort.
Statistical timing analysis, which accounts for process variations and reports statistical distributions, is an increasingly important technology for IC design at 65 nanometers and below. One problem, however, has been the difficulty of characterizing statistical libraries. Another is the lack of a standard statistical library format, a problem that Si2 is addressing through its Open Modeling Coalition (OMC).
Altos claims to have new technology, which it first announced last July, that speeds library characterization by an order of magnitude (see July 3, 2006, page 1). Last year the company introduced Liberate, a characterization tool for traditional, static timing analysis. This week Altos is fulfilling its original promise by rolling out Variety, which applies the same technology to statistical libraries.
"Statistical timing has great potential, but to enable that potential, you need models," said Altos CEO Jim McCanny. "Variety allows you to generate models accurately and efficiently. We think we can generate statistical models in about the same time that people take to generate traditional [static] models today."
That's a bold claim, given the extra work it takes to generate statistical models. First, McCanny noted, statistical libraries track variations over multiple parameters, and second, random variations require an analysis of every transistor in a cell. It's not uncommon, he said, for statistical models to take 20 or even 50 times longer to generate than static models. "We break this barrier enough so that people can start looking at putting statistical analysis in their flows," he said.
Meanwhile, Altos has donated a copy of Variety to the OMC's statistical timing working group. Oscar Siguenza, director at Virage Logic and chair of the working group, said it will be used to help create a "reference flow" for statistical characterization and modeling. This will help the working group meet its goal of coming up with a draft statistical library format standard by April, he said.
"What we are intending to do is a proof of concept for the techniques that vendors will productize," Siguenza said. Variety, he said, "would be the characterization engine for generating the formats that are needed." While statistical timing analysis providers have their own characterization tools--including OMC working group members Cadence Design Systems, Extreme DA and Magma Design Automation--Variety has the advantage of being "relatively agnostic when it comes to different tool flows out there," Siguenza said.
Altos has a strong interest in seeing the OMC succeed. Because there's no standard statistical library format today, Altos must work individually with each statistical timing provider to ensure Variety will work with that vendor's tool. As such, Altos is currently working with Cadence, Extreme DA and Synopsys. Those relationships are both cooperative and competitive, however, because all the vendors have their own library tools.