"The key to verification is good enginering," said John Andrusiak, a member of the technical staff at Sun Microsystems' Scalable Systems Group. He warned that verification can't overcome bad design, and urged designers not to create unverifiable designs.

"You can't verify today's designs 100 percent. Designs should be built so that when they fail, they can recover gracefully," Andrusiak said.

Qasim Shami, LSI Logic's director of engineering for the Communications Division, said what's needed are "independent design and verification teams, but a concurrent design and verification development environment."

Chip architects need to be "continuously involved in the design process to constantly watch the design as it progresses," said Shami. From the start, designs need a clear definition of where interfaces should be split between blocks of the chip.

Formal verification tools are no help. Eighteen to 20 months ago, Sun implemented formal verification tools that were not up to the task, said Andrusiak. "We had to go back to functional verification."

LSI Logic's Shami concurred: " Formal verification tools are not ready for prime time."

The key to assuring comprehensive IC verification is "to get people to think that nothing works unless it is tested," said Somdipta Basu Roy, senior member technical staff at Texas Instruments' Wireless Terminal Business unit. "There is no magic to verfying your design. Try to stay away from cycle-accurate checkers and provide feedback to the spec team of the test performance, bandwidth and latency as early as possible."

As for verification methodologies, Andrusiak said Sun relies on a constrained random testbench using an object-oriented, channel-based simulation methodology. "Assertions are good for low-level individual blocks," said Andrusiak.

"In the end you need to accept that the chip cannot be verified 100 percent and you need to rely on software to bail out the hardware," said Shami. "In most applications 99.95 percent is enough."

That's why older, more reliable technologies are used in mission-critical aerospace and medical electronics applications, said Shami.