Power Architecture and Energy Management

The latest version of the ISA specifications for the Power architecture, Power ISA v.2.06 published Feb last year, introduces mechanisms in the architecture that help power management in chips based on the spec. Besides decreasing the energy demand in general, processors to be used in embedded applications need power management such that things can be done at as low a power demand as possible. Overall architecture has to take the low consumption into account and layouts made accordingly, of course.


Most these sophisticated chips use dynamic circuitry that draw more power as the clock speed goes up. So, sections of hardware circuitry that are not needed during a particular use, can have clock to these sections choked off. This is a well known technique and is being introduced in processor chips for some time. This specification also introduces  "clock gating" as a tool to manage power. Overall the core frequency can be manipulated to manage consumption. For example, it can be pushed up when the processor has to handle heavy processing load, while it can be reduced in other situations. Software can dynamically increase or decrease the core’s clock frequency while the rest of the system keeps operating at an earlier value.


The Power ISA v.2.06 allows for power management on hypervisor and virtualization on single and multi-core processor implementations. A dynamic energy management lets parts of the core to operate and other parts not required to be power gated. For example execution units in the processor pipeline could be power-gated when idle. The architecture offers software-selectable power-saving modes. These modes may reduce the functionality in some areas, such as limiting cache and bus-snooping operations. In some operation scenarios you may turn off all functional units except for interrupts. This architecture now also enables execution of an instruction that can shut off the chip and let it wake up only on an external event.  read the following article for further details.

Energy Management in Power Architecture