Tham khảo tài liệu 'adaptive techniques for dynamic processor optimization theory and practice episode 2 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 232 Steve Furber Jim Garside This adaptivity to environmental conditions means that voltage scaling on self-timed circuits is trivially easy to manage. All that is needed is to vary the voltage the operating speed and power will adapt automatically. Similarly the circuits will slow down if they become hot but they will still function correctly. This has been demonstrated repeatedly with experimental asynchronous designs. A great deal is said about voltage scaling elsewhere in this book so it is sufficient here to note that most of the complexity of voltage scaling is in the clock control system which ceases to be an issue when there is no clock to control Instead this chapter concentrates on other techniques which are facilitated by the asynchronous style. Asynchronous Adaptation to Workload Power - or rather energy - efficiency is important in many processing applications. As described elsewhere one way of reducing the power consumption of a processor is reducing the clock or instruction frequency and energy efficiency may then also be improved by lowering the supply voltage. Of course if the processor is doing nothing useful the energy efficiency is very poor and in this circumstance it is best to run as few instructions as possible. In the limit the clock is stopped and the processor sleeps pending a wake-up event such as an interrupt. Synchronous processors sometimes have different sleep modes including gating the clock off but keeping the PLL running shutting down the PLL and turning the power off. The first of these still consumes noticeable power but allows rapid restart the second is more economical but takes considerable time to restart as the PLL must be allowed to stabilise before the clock is used. This is undesirable if for example all that is required is the servicing of interrupts in a real-time system. It is a software decision as to which of these modes to adopt needless to say this software also imposes an energy overhead. An asynchronous .
