ABSTRACT
The Unified Power Format (UPF), currently undergoing standardization efforts by the IEEE P1801 Low Power Working Group, is a proposal for the specification of aspects of hardware designs relating to their power adaptation facilities. UPF is concerned with two separate but related issues. First, it enables the explicit specification of the aspects of a design relating to its power dissipation, such as the system's different power supply rails and the associated domains running off these supplies, different threshold voltage domains in a multi-Vt technology, the system's operations states with different power dissipation properties, and the semantics of system behavior when in different power states (e.g., whether registers keep their state when a supply rail is gated); this is a design issue, and is addressed in UPF by the UPF commands for specifying low-power design intent. Second, UPF enables the specification of information pertaining to power estimation results from hardware designs; this is a measurement issue, and is addressed in UPF by the forward and backward Switching Activity Interchange Format (SAIF) files.

From the viewpoint of design, UPF enables designers to specify the interconnection of system components as they pertain to power dissipation. For example, a UPF specification for an embedded processor in which the processor core operates off a different voltage rail from its peripherals might define two power supply nets in a UPF description, corresponding to two different power domains within the UPF specification, and may define the core and peripherals to be each connected to one of these. UPF encapsulates the semantics of a system's power-related design and measurement issues into a separate specification in which the components have a direct correspondence to items in the hardware logic specification.

The specification of this logical structure of power-dissipation- related design and runtime information separately in a UPF description aids activities such as simulation, where the power states of different system components might be deduced from analysis of the UPF description in the context of a given workload.

The importance of UPF to integrated circuit and system designers is obvious, with the increasing criticality of understanding the power-dissipation behavior of systems, as well as the increasing use of multiple supply voltages in existing designs and design starts. What does UPF mean for the academic research community? Research targeted at design automation of low-power systems, whether focusing on the system-level, circuit-level, layout, or elsewhere, may be able to build new kinds of algorithms, and their implementations in tools, that take advantage of the coherent isolation of power-related concepts in UPF. For example, since the UPF specification for a system can be used to provide a detailed description of its power supply network and power states independent of the disclosure of its logic-level implementation, UPF specifications may be provided by semiconductor device vendors (e.g., for a microcontroller, microprocessor, or integrated system-on-chip), enabling the evaluation of power consumption behavior under different workloads. This will however require appropriate tools for "simulating" or otherwise analyzing UPF specifications, and a means of specifying such workloads to "drive" the specifications, if relevant.

UPF is described in detail in the ``Unified Power Format Standard, version 1.0'', available online at
http://www.accellera.org/activities/p1801_upf/.
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