Although SystemC establishes a language standard, users are having difficulty integrating SystemC TLMs from outside their companies into their design flows. The OSCI TLM 1.0 standard defines a set of APIs for transaction-level communications, but does not define the content of the transactions. That's a task left for the TLM 2.0 standard that's now under development.

Emil Girczyc, president and CEO of Summit Design, noted that effective ESL depends on "accurate, interoperable" intellectual property (IP). But it can still take two to three man-months for a company to integrate a vendor's SystemC model into its own TLM simulation system, he said.

"We've personally seen three different models written for three versions of OSCI [SystemC simulator], which the customer was trying to integrate into one simulator," Girczyc said. "We need a flow where we can get a model up and running a lot more quickly."

Grant Martin, chief scientist at Tensilica Inc., noted that Tensilica customers often use that company's processors along with other IP, and need to simulate it all together. But TLM standards don't yet provide ESL model interoperability, he said. Martin noted that OSCI TLM 1.0 defines a simple transport for read and write, but does not provide a reasonable set of transaction types, debug access modes, performance modeling, and simulation semantics.

Ken Vu, performance analysis and services manager for IBM's system and technology group, also noted the lack of standards. "We expect there's a lot more work to be done before IP can be fully interoperable," he said. "We're working with the EDA vendors to ensure IP compatibility."

"The most important thing about standards is the ability to interoperate and certify components so they all work together," said Michael Uhler, CTO of MIPS Technologies. "For our customers, it's important to create models and they have to interoperate with each other," said Drew Wingard, Sonics CTO.

"It's a good sign we've settled on SystemC, but there are still challenges with different versions," Wingard said. "We still have more problems than the RTL world had." Among them, he said, is the need to compile models separately for different operating systems.

Mike Meredith, vice president of technical marketing for Forte Design and president of OSCI, brought some good news. He noted that OSCI's TLM working group has released a timetable for the development of version 2.0.

This timetable calls for a September public view of an initial library that includes the programmer's view (PV) and programmer's view with timing (PVT) data structures, along with an analysis interface. A 2.1 draft release next spring will add a debugging interface. OSCI is hoping to have a 2.1 language reference manual (LRM) and official release by the 2007 Design Automation Conference in June.

Meredith warned, however, against an "impatience for standards." It's important to do enough innovation before trying to build a standard, he said — and wide variations are actually good, because it results in a wide selection of choices.

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