Torrellas isn’t the first person to build patchable hardware; Crusoe and Itanium microprocessors, used in some laptop and desktop computers, can also be patched. But Torrellas says that Phoenix offers a more efficient approach. Crusoe microprocessors, which are made by Transmeta, have an additional level of complexity: special software that translates all commands. Defects are fixed by changing the way commands are interpreted. The process works, but Torrellas says it slows down the chip far more than Phoenix does. Itanium chips, which were developed jointly by Intel and Hewlett-Packard, are also relatively inefficient when patched, according to Torrellas. Moreover, a wider variety of problems can be fixed on a Phoenix-enabled chip.
Phoenix can’t fix all hardware defects, but Torrellas says it can recover from most critical bugs, such as those that would crash a computer. The Phoenix team performed a detailed analysis of past problems with AMD, Intel, IBM, and Motorola chips to determine which issues it should address first. Consequently, Phoenix is designed to focus on particularly problematic areas, such as the memory subsystem.
Whether Torrellas’s technology will make its way into commercial computers, however, is uncertain. “Their analysis of where bugs occur is excellent,” says Wilson Snyder, a principal engineer for the high-performance computer-hardware manufacturer SiCortex, based in Maynard, MA. “It provides a good, detailed look at signals that should be analyzed to discover bugs.” Hardware manufacturers could learn from the basic research behind Phoenix, Snyder says, and use it to eliminate hardware problems before chips hit the stores. But he questions whether manufacturers would ever implement Phoenix itself. Adding Phoenix onto an existing chip would take time and money, he points out.
Torrellas believes manufacturers will be amenable to a system like Phoenix, particularly as hardware problems grow. “Chip designs are becoming more and more complicated,” he says. “Bigger teams are designing the processors, so there is more scope for miscommunication.” The more problems pop up, the more manufacturers will be willing to consider new solutions.