Amulet microprocessors are asynchronous (clockless) implementations of the ARM 32-bit RISC architecture. Their asynchronous control framework has positive benefits for low-power applications because it reduces activity to the minimum required to perform a task, whereas a clock inevitably incurs wasteful activity.
Citation:
Steve B. Furber, Aristides Efthymiou, Jim D. Garside, David W. Lloyd, Mike J.G. Lewis, Steve Temple, "Power Management in the Amulet Microprocessors," IEEE Design and Test of Computers, vol. 18, no. 2, pp. 42-52, Mar./Apr. 2001, doi:10.1109/54.914617