Is it time for clockless chips? [Asynchronous processor chips]

Vendors are revisiting an old concept - the clockless chip - as they look for new processor approaches to work with the growing number of cellular phones, PDAs, and other high-performance, battery-powered devices. Clockless processors, also called asynchronous or self-timed, don't use the oscillating crystal that serves as the regularly "ticking" clock that paces the work done by traditional synchronous processors. Rather than waiting for a clock tick, clockless-chip elements hand off the results of their work as soon as they are finished. However, clockless chips still generate concerns - such as a lack of development tools and expertise as well as difficulties interfacing with synchronous chip technology - that proponents must address before their commercial use can be widespread.