What Controls the Power of a Platform?

The Confusing Platform Definition

The term “platform” means different things to different people. At one level a platform is a processor core with its associated memories. At a higher level it may be a processor core with a few peripheral modules. At an even higher level it can be a collection of components connected together with software to create an end product, which is the definition I’m using for this discussion.

Voltage Domains

There are typically multiple voltage domains in a platform, each catering to the differing requirements of the platform component, such as basebands, application processors, memories and displays. For high current consuming components, a switching regulator is desired for efficient power conversion. So do the regulators control the power of a platform? No … the regulators only source the power.

Hardware Components

The hardware components in a platform are typically designed using low power techniques, such as clock gating, reduced power modes and state retention power gating. A great deal of thought is put into the component architectures to ensure that the low-power techniques can be used and the transitions between low-power modes are smooth. So do the hardware components control the power of a platform? No … the hardware components only provide means to effectively use the power.

So what controls the power of a platform?

The answer revolves around the word “control.” The software controls the behavior and operation of the platform, and ultimately, the platform’s power. The software can either utilize the platform’s low power techniques, or it can ignore those techniques and operate at the highest voltage and frequency of the hardware. In both cases, the use case will be performed, but one will be more power efficient than the other.

When putting together a power-sensitive product, software control for power minimization is a critical optimization step that is often skipped due to time-to-market constraints. Ideally, the hardware and software should be developed interactively to create a platform with the lowest power consumption. However, in most cases, this is not possible since off-the-shelf components are used. So, it is important to select components that have the right low-power hardware capabilities and software that is written to take advantage of all the low-power hardware in the components.

– Chris