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Non-uniform memory access
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<p>Non-uniform memory access (NUMA) is a <a href="/facts/Computer_storage/wPHKFpdx">computer memory</a> design used in <a href="/facts/Multiprocessing/aDCfehDQ">multiprocessing</a>, where the memory access time depends on the memory location relative to the processor. Under NUMA, a processor can access its own <a href="/facts/Local_memory/Gg0UkuqW">local memory</a> faster than non-local memory (memory local to another processor or memory shared between processors). NUMA is beneficial for workloads with high memory <a href="/facts/Locality_of_reference/fYFKDv5q">locality of reference</a> and low <a href="/facts/Lock_contention/e3a9gnJT">lock contention</a>, because a processor may operate on a subset of memory mostly or entirely within its own cache node, reducing traffic on the memory bus. </p><p>NUMA architectures logically follow in scaling from <a href="/facts/Symmetric_multiprocessing/T9CahUsN">symmetric multiprocessing</a> (SMP) architectures. They were developed commercially during the 1990s by <a href="/facts/Unisys/y49ddC6b">Unisys</a>, <a href="/facts/Convex_Computer/e2W7PJe5">Convex Computer</a> (later <a href="/facts/Hewlett-Packard/abuNSYNu">Hewlett-Packard</a>), <a href="/facts/Honeywell/qjkujlwJ">Honeywell</a> Information Systems Italy (HISI) (later <a href="/facts/Groupe_Bull/tlbdToLt">Groupe Bull</a>), <a href="/facts/Silicon_Graphics/DKvkrfLX">Silicon Graphics</a> (later <a href="/facts/Silicon_Graphics_International/IfrJDnHP">Silicon Graphics International</a>), <a href="/facts/Sequent_Computer_Systems/kTLC7aja">Sequent Computer Systems</a> (later <a href="/facts/IBM/QszA7nwd">IBM</a>), <a href="/facts/Data_General/EEABV3Gu">Data General</a> (later <a href="/facts/EMC_Corporation/yYovmS66">EMC</a>, now <a href="/facts/Dell_Technologies/QolHjMPw">Dell Technologies</a>), <a href="/facts/Digital_Equipment_Corporation/ztxs6keA">Digital</a> (later <a href="/facts/Compaq/6LuhWTE7">Compaq</a>, then <a href="/facts/Hewlett-Packard/abuNSYNu">HP</a>, now <a href="/facts/Hewlett_Packard_Enterprise/d9NbClDt">HPE</a>) and <a href="/facts/International_Computers_Limited/2ztan410">ICL</a>. Techniques developed by these companies later featured in a variety of <a href="/facts/Unix-like/YAKrAxzd">Unix-like</a> <a href="/facts/Operating_system/8XTuvMh2">operating systems</a>, and to an extent in <a href="/facts/Windows_NT/EtccWvxQ">Windows NT</a>. </p><p>The first commercial implementation of a NUMA-based Unix system was[<i>where?</i>][<i>when?</i>] the Symmetrical Multi Processing XPS-100 family of servers, designed by Dan Gielan of VAST Corporation for <a href="/facts/Honeywell_Information_Systems/qjkujlwJ">Honeywell Information Systems</a> Italy. </p>