execution unit

{{Short description|Part of a CPU which performs the operations instructed by the program}}

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In computer engineering, an execution unit (E-unit or EU) is a part of a processing unit that performs the operations and calculations forwarded from the instruction unit.{{Cite web |title=Execution Model Overview |url=https://www.intel.com/content/www/us/en/docs/oneapi/optimization-guide-gpu/2024-1/execution-model.html |access-date=2024-06-23 |website=Intel |language=en}} It may have its own internal control sequence unit (not to be confused with a CPU's main control unit), some registers,{{Cite web |title=AMD Instinct™ MI100 microarchitecture — ROCm Documentation |url=https://rocm.docs.amd.com/en/docs-6.0.0/conceptual/gpu-arch/mi100.html#microarchitecture |access-date=2024-06-23 |website=rocm.docs.amd.com}} and other internal units such as an arithmetic logic unit,{{Cite web |title=Intel® Iris® Xe GPU Architecture |url=https://www.intel.com/content/www/us/en/docs/oneapi/optimization-guide-gpu/2023-0/intel-iris-xe-gpu-architecture.html |access-date=2024-06-23 |website=Intel |language=en}} address generation unit, floating-point unit, load–store unit, branch execution unit{{cite web |last=Kanter |first=David |date=November 13, 2012 |title=Intel's Haswell CPU Microarchitecture |url=https://www.realworldtech.com/haswell-cpu/4/ |website=Real World Tech}} or other smaller and more specific components, and can be tailored to support a certain datatype, such as integers or floating-points.[https://web.archive.org/web/20131231145405/http://people.cs.umass.edu/~weems/CmpSci535/Discussion10.html "Execution Unit" discussion from the University of Massachusetts Amherst], archived on the Wayback Machine

It is common for modern processing units to have multiple parallel functional units within its execution units, which is referred to as superscalar design.{{Cite web |last=Cohen |first=William |date=2016-03-14 |title=Superscalar Execution |url=https://developers.redhat.com/blog/2016/03/14/superscalar-execution |access-date=2024-06-23 |website=Red Hat Developer |language=en}} The simplest arrangement is to use a single bus manager unit to manage the memory interface and the others to perform calculations. Additionally, modern execution units are usually pipelined.