Tuesday, April 10, 2007

Efficient Hardware Repair

Researchers devise a new way to patch hardware like software, without slowing processors.

By Rachel Ross

Patching processors: The large chip in the center of the circuit board (above) can be repeatedly programmed with new information on hardware defects. Credit: Josep Torrellas

Defective chips can be expensive for computer manufacturers, especially when the hardware is recalled. They can also be a hassle for consumers, as they can cause computers to miscalculate, slow down, and, sometimes, crash. Computer-science professor Josep Torrellas thinks he has found a better way to deal with faulty chips: an efficient repair mechanism that treats hardware more like software, by fixing bugs with downloadable patches. His system is still in development, but he says it could ultimately make chip production faster and cheaper.

"We know how to fix software really easily," says Torrellas, a professor at the University of Illinois at Urbana Champaign. "We send patches around. Wouldn't it be nice if you could simply get another patch from the vendor to fix your hardware?"

The centerpiece of Torrellas's system is Phoenix: special hardware that resides on the chip and can be programmed to detect defects and implement solutions. The prototype hardware consists of a standard semiconductor device called a field programmable gate array. While such devices are typically a bit slower than chips made for a single application, they have the advantage of being easily reprogrammed--an essential feature of Torrellas's system.

In some ways, the system works much like antivirus software, which uses downloaded virus information to identify and eliminate new threats. Similarly, if a defect is discovered on a Phoenix-enabled chip, the manufacturer would automatically transmit the patch to all machines that might be affected. The patch contains a defect signature outlining the specific events that lead to the hardware problem. (For example, when the processor executes certain instructions and stores something in a particular part of the computer's memory, the computer might crash.) Once installed, the patch reprograms the Phoenix device so that it monitors the chip for the defect signature and alters the computer's processes to prevent a crash.

Torrellas says that most chips have dozens of defects, although not all are catastrophic: some simply result in miscalculations, for example. Today, manufacturers often deal with hardware problems by disabling features that are found to be defective. "In the end, the user loses functionality," Torrellas says. When no solution can be found and the problem is critical, manufacturers recall the chips at their expense. A patching scheme would avoid those costs and maintain the chip's functionality.

A Phoenix-enabled chip would also have a shorter time to market, according to Torrellas. Manufacturers could skip the last few weeks of testing, knowing that ultimately, they can solve problems with patches. "If they know that they could fix the problems later on, they could beat the competition to market," he says.