Editing Non-uniform memory access (section)

{{Short description|Computer memory design used in multiprocessing}}

[[File:HP Z820 motherboard.jpg|thumb|The motherboard of an [[HP Z|HP Z820]] workstation with two CPU sockets, each with their own set of eight [[DIMM]] slots surrounding the socket.]]
'''Non-uniform memory access''' ('''NUMA''') is a [[computer storage|computer memory]] design used in [[multiprocessing]], where the memory access time depends on the memory location relative to the processor. Under NUMA, a processor can access its own [[local memory]] faster than non-local memory (memory local to another processor or memory shared between processors).<ref>{{FOLDOC|Non-uniform+memory+access}}</ref> NUMA is beneficial for workloads with high memory [[locality of reference]] and low [[lock contention]], because a processor may operate on a subset of memory mostly or entirely within its own cache node, reducing traffic on the memory bus.<ref name="nyu-numa">{{Cite web
 | url = http://cs.nyu.edu/~lerner/spring10/projects/NUMA.pdf
 | title = Non-Uniform Memory Access (NUMA)
 | date = 2010-05-04
 | access-date = 2014-01-27
 | author1 = Nakul Manchanda
 | author2 = Karan Anand
 | publisher = New York University
 | archive-url = https://web.archive.org/web/20131228092942/http://www.cs.nyu.edu/~lerner/spring10/projects/NUMA.pdf
 | archive-date = 2013-12-28
 | url-status = dead
 }}</ref>

NUMA architectures logically follow in scaling from [[symmetric multiprocessing]] (SMP) architectures. They were developed commercially during the 1990s by [[Unisys]], [[Convex Computer]] (later [[Hewlett-Packard]]), [[Honeywell]] Information Systems Italy (HISI) (later [[Groupe Bull]]), [[Silicon Graphics]] (later [[Silicon Graphics International]]), [[Sequent Computer Systems]] (later [[IBM]]), [[Data General]] (later [[EMC Corporation|EMC]], now [[Dell Technologies]]), [[Digital Equipment Corporation|Digital]] (later [[Compaq]], then [[Hewlett-Packard|HP]], now [[Hewlett Packard Enterprise|HPE]]) and [[International Computers Limited|ICL]]. Techniques developed by these companies later featured in a variety of [[Unix-like]] [[operating system]]s, and to an extent in [[Windows NT]].

The first commercial implementation of a NUMA-based Unix system was{{where|date=January 2022}}{{when|date=March 2023}} the Symmetrical Multi Processing XPS-100 family of servers, designed by Dan Gielan of VAST Corporation for [[Honeywell Information Systems]] Italy.