Heterogeneous computing

Heterogeneous computing refers to systems that use more than one kind of processor or cores. These systems gain performance or energy efficiency not just by adding the same type of processors, but by adding dissimilar coprocessors, usually incorporating specialized processing capabilities to handle particular tasks.

Usually heterogeneity in the context of computing referred to different instruction set architectures (ISA), where the main processor has one and the rest have another, usually a very different architecture (maybe more than one), not just a different microarchitecture (floating point number processing is a special case of this not usually referred to as heterogeneous). E.g. ARM big.LITTLE is an exception where the ISAs of cores are the same and heterogeneity refers to the speed of different microarchitectures of the same ISA, then making it more like a symmetric multiprocessor (SMP).

In the past heterogeneous computing meant different ISAs had to be handled differently, while a modern example, Heterogeneous System Architecture (HSA) systems, eliminate the difference (for the user); use multiple processor types (typically CPUs and GPUs), usually on the same integrated circuit, to provide the best of both worlds: general GPU processing (apart from its well-known 3D graphics rendering capabilities, it can also perform mathematically intensive computations on very large data sets), while CPUs can run the operating system and perform traditional serial tasks.

The level of heterogeneity in modern computing systems is gradually increasing as further scaling of fabrication technologies allows for formerly discrete components to become integrated parts of a system-on-chip, or SoC. For example, many new processors now include built-in logic for interfacing with other devices (SATA, PCI, Ethernet, USB, RFID, Radios, UARTs, and memory controllers), as well as programmable functional units and hardware accelerators (GPUs, cryptography co-processors, programmable network processors, A/V encoders/decoders, etc.).

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