Application Processors

An Application Processor (AP) is the main processing unit of a system, commonly designed as a System on Chip (SoC). APs are sometimes also considered microprocessors, as opposed to microcontrollers. Another regularly used term is Central Processing Unit (CPU). While design approaches and names have changed over the years, psi-spec is concerned with the kind of processors that feature a Memory Management Unit (MMU) and DRAM, allowing for many concurrent tasks and processing large amounts of data.

System on Chip

An SoC integrates processing units with IO peripherals via internal system buses and networks, all packaged into one chip.

Common buses are defined by the AMBA standards, the WISHBONE Interconnect Architecture, and CoreConnect. Some vendors have their own designs, such as AMD's Infinity Fabric. A bus is generally a set of physical interfaces and corresponding protocols.

A Network on a Chip (NoC) improves the scalability of SoC components and its power efficiency over shared buses.

Parts of an SoC are called blocks.