Bug Catching

Debugging normally involves putting a chip through a battery of tests to identify spots that are likely to fail and to give engineers a chance to fix problems before the chips go into mass production. As chip-making companies as push the functionality of their hardware, this becomes increasingly complicated.

Subhasish Mitra, professor of electrical engineering and computer science at Stanford and colleagues have developed a method that uses a small number (about 1 percent) of the transistors on a chip to record a log of chip activity--the instructions that pass through the chip's circuits. This log can be extracted from the chip, dumped into a computer, and analyzed to find out where the bugs are.

"It's enormously expensive to diagnose where chips are failing," says Rob Rutenbar, professor of computer science at the University of Illinois, who wasn't involved with the research. As the features on microprocessors get smaller, Rutenbar says, "people worry more about wear-out and reliability issues."