
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.
Heterogeneity.
Usually heterogeneity in the context of computing referred to different instruction-set architectures (ISA), where the main processor has one and other processors 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).
In the past heterogeneous computing meant different ISAs had to be handled differently, while in a modern example, Heterogeneous System Architecture (HSA) systems eliminate the difference (for the user) while using 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 the GPU's 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.).
Recent findings show that a heterogeneous-ISA chip multiprocessor that exploits diversity offered by multiple ISAs can outperform the best same-ISA homogeneous architecture by as much as 21% with 23% energy savings and a reduction of 32% in Energy Delay Product (EDP). AMD's 2014 announcement on its pin-compatible ARM and x86 SoCs, codename Project Skybridge,
suggested a heterogeneous-ISA (ARM+x86) chip multiprocessor in the making.
Heterogeneous CPU topology.
A system with heterogenous CPU topology is a system where the same ISA is used, but the cores themselves are different in speed. The setup is more similar to a symmetric multiprocessor. (Although such systems are technically asymmetric multiprocessors, the cores do not differ in roles or device access.)
A common use of such topology is to provide better power efficiency in mobile SoCs. ARM big.LITTLE is the prototypical case, where faster high-power cores are combined with slower low-power cores. Apple has produced Apple silicon ARM cores with similar organization. Intel has also produced hybrid x86 cores codenamed Lakefield, although not without major limitations in instruction set support.
Alder Lake uses small and big cores.
Challenges.
Heterogeneous computing systems present new challenges not found in typical homogeneous systems. The presence of multiple processing elements raises all of the issues involved with homogeneous parallel processing systems, while the level of heterogeneity in the system can introduce non-uniformity in system development, programming practices, and overall system capability. Areas of heterogeneity can include:
Example hardware.
Heterogeneous computing hardware can be found in every domain of computing—from high-end servers and high-performance computing machines all the way down to low-power embedded devices including mobile phones and tablets.