CprE458558Real-TimeSystems(G.Manimaran)详解.pptVIP

* * * * * * * * * CprE 458/558: Real-Time Systems (G. Manimaran) * Energy Aware Real Time SystemsAcknowledgments: Gathala Sudha Anil KumarKi-Sung Koo(former TAs) CprE 458/558: Real-Time Systems (G. Manimaran) * Introduction Energy consumption is an important issue in embedded systems. Mobile and portable devices, laptops Mobile and Intelligent systems: Digital camcorders, cellular phones, and portable medical devices. Sensor network applications Embedded devices play prominent roles in a variety of applications medical sensors in human body. Signaling sensors in war fields. A typical networked embedded system consists of: Computing subsystem -- driven by an embedded processor operated by a RTOS. Communication subsystem -- consists of a radio chipset driven by a firmware. Micorprocessor, Digital Signal Processor (DSP) Radio, RF amplifiers, A-to-D D-to-A ckts A typical Embedded System Battery Computing Subsystem (Driven by RTOS) Communication Subsystem (Driven by Firmware) Introduction CprE 458/558: Real-Time Systems (G. Manimaran) * Important Facts (1) The peak computing rate needed is much higher than the average throughput that must be sustained; High performance is needed only for a small fraction of time, while for the rest of time, a low-performance, a low-power processor would suffice. CprE 458/558: Real-Time Systems (G. Manimaran) * Workload Profile Time Work load Peak Computing Rate is needed Average rate would suffice CprE 458/558: Real-Time Systems (G. Manimaran) * Important Facts (2) Processors are based on CMOS logic -- Static power + Dynamic power Dynamic power (due to switching activity) P α V2 . f V α f V: voltage; P: power; E: Energy E = P * Tcc Tcc = CC/f Ei = K .cci . f2 Where Tcc : execution time; CCi : # clock cycles of task Ti. f : frequency at which Ti is run. CprE 458/558: Real-Time Systems (G. Manimaran) * Variable Voltage Processors Modern processors operate at multiple freque