Symmetric versus asymmetric multiprocessing

Over the past decades, many systems were created which contained multiple processing units. These can be broadly divided into Symmetric Multiprocessing (SMP) and Asymmetric Multiprocessing (AMP) systems.

AMP's main defining feature is that a second processor is attached as a peripheral to the primary CPU. This means that it cannot run control software, but only user applications. This approach has also been used to connect CPUs using a different architecture to allow one to, for example, run x86 applications on an Amiga, 68k-based system.

With an SMP system, each of the CPUs are peers having access to the same hardware resources, and set up in a cooperative fashion. Initially, SMP systems involved multiple physical CPUs, but later, multiple processor cores got integrated on a single CPU die:

With the proliferation of multi-core CPUs, SMP is the most common type of processing outside of embedded development, where uniprocessing (single core, single processor) is still very common.

Technically, the sound, network, and graphic processors in a system can be considered to be asymmetric processors related to the CPU. With an increase in General Purpose GPU (GPGPU) processing, AMP is becoming more relevant.