Multi-channel memory architecture: Difference between revisions

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{{Short description|Computer memory architecture}}

<nowiki>[[fa:معماری حافظه چند کاناله]]</nowiki>{{multiple issues|

{{confusing |date=October 2011}}

{{refimprove|date=January 2014}}

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In the fields of [[digital electronics]] and [[computer hardware]], '''multi-channel memory architecture''' is a technology that increases the data transfer rate between the [[DRAM]] memory and the [[memory controller]] by adding more channels of communication between them. Theoretically, this multiplies the data rate by exactly the number of channels present. Dual-channel memory employs two channels. The technique goes back as far as the 1960s having been used in [[IBM System/360 Model 91]] and in [[CDC 6600]].<ref name="JacobNg2007">{{cite book| first1=Bruce | last1 = Jacob | first2 = Spencer | last2 = Ng | first3=David | last3 = Wang|title= Memory systems: cache, DRAM, disk|year = 2007 | publisher = Morgan Kaufmann|isbn=978-0-12-379751-3|page= 318}}</ref>

Modern high-end desktop and workstation processors such as the [[Advanced Micro Devices|AMD]] [[Ryzen Threadripper]] series and the [[Intel]] [[List of Intel Core i9 processors|Core i9 Extreme Edition]] lineup support quad-channel memory. Server processors from the AMD [[Epyc]] series and the Intel [[Xeon]] platforms give support to memory bandwidth starting from quad-channel module layout to up to octa12-channel layout.<ref>{{Citecite web |lastlast1=jpringleShilov |datefirst1=SeptemberAnton 12, 2017|title=BenchmarkingAMD Epyc,Confirms Ryzen,Twelve andDDR5 Xeon:Memory TyrannyChannels ofFor Zen 4 EPYC CPUs Memory|url=https://www.myromstomshardware.orgcom/forumnews/viewtopic.php?p=18295|urlamd-statusconfirms-12-ddr5-memory-channels-on-genoa |website=liveTom's Hardware |access-date=April9 23,December 2021 |websitepublisher=[[RegionalFuture OceanUS ModelingInc System]]|access-date=22 April 2024}}</ref> In March 2010, AMD released [[Socket G34]] and Magny-Cours Opteron 6100 series<ref name = Opteron6100>{{cite web | publisher = AMD | title = Opteron 6000 Series Platform Quick Reference Guide | url = http://sites.amd.com/us/documents/48101a_opteron%20_6000_qrg_rd2.pdf | access-date = 2012-10-15 | archive-url = https://web.archive.org/web/20120512170219/http://sites.amd.com/us/Documents/48101A_Opteron%20_6000_QRG_RD2.pdf | archive-date = 2012-05-12 | url-status = dead }}</ref> processors with support for quad-channel memory. In 2006, Intel released chipsets that support quad-channel memory for its [[LGA771]] platform<ref>{{Citation | url = http://ark.intel.com/products/27746/Intel-5000P-Memory-Controller | publisher = Intel | title = 5000P memory controller}}.</ref> and later in 2011 for its [[LGA2011]] platform.<ref>{{Citation | url = http://www.techpowerup.com/138087/Intel-LGA2011-Socket-X68-Express-Chipset-Pictured.html | title = Intel LGA2011 socket x68 express chipset pictured | date = 10 January 2011 | publisher = Tech power up}}.</ref> Microcomputer chipsets with even more channels were designed; for example, the chipset in the [[AlphaStation]] 600 (1995) supports eight-channel memory, but the [[backplane]] of the machine limited operation to four channels.<ref>{{Citation | journal = HP | url = http://www.hpl.hp.com/hpjournal/dtj/vol7num1/vol7num1art7.txt | title = The Design and Verification of the AlphaStation 600 5-series Workstation | volume = 7 | number = 1 | author1 = John H. Zurawski | author2 = John E. Murray | author3 = Paul J. Lemmon | access-date = 2011-10-19 | archive-date = 2021-02-25 | archive-url = https://web.archive.org/web/20210225050210/https://www.hpl.hp.com/hpjournal/dtj/vol7num1/vol7num1art7.txt | url-status = dead }}.</ref> <!-- TO-DO: Cite a machine where they actually used 8 channels. -->

== Dual-channel architecture ==

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=== Operation ===

Dual-channel architecture requires a dual-channel-capable motherboard and two or more [[DDR SDRAM|DDR]], [[DDR2 SDRAM|DDR2]], [[DDR3 SDRAM|DDR3]], [[DDR4 SDRAM|DDR4]], or [[DDR5 SDRAM|DDR5]] memory modules. The memory modules are installed into matching banks, each of which belongs to a different channel. The motherboard's manual will provide an explanation of how to install memory for that particular unit. A matched pair of memory modules may usually be placed in the first bank of each channel, and a different-capacity pair of modules in the second bank.<ref name= "Kingston520DDR">{{cite web | publisher = Infineon Technologies North America and Kingston Technology |date=September 2003 | url = http://www.kingston.com/newtech/MKF_520DDRwhitepaper.pdf | archive-url = https://web.archive.org/web/20110929024052/http://www.kingston.com/newtech/MKF_520DDRwhitepaper.pdf | title = Intel Dual-Channel DDR Memory Architecture White Paper | edition = Rev. 1.0 | format = PDF, 1021&nbsp;[[kilobyte|KB]] | access-date = 2007-09-06 | archive-date = 2011-09-29}}</ref> Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module. Some motherboards, however, have compatibility issues with certain brands or models of memory when attempting to use them in dual-channel mode. For this reason, it is generally advised to use identical pairs of memory modules, which is why most memory manufacturers now sell "kits" of matched-pair DIMMs. Several motherboard manufacturers only support configurations where a "matched pair" of modules are used. A matching pair needs to match in:

* Capacity (e.g. 1024&nbsp;MB). Certain Intel chipsets support different capacity chips in what they call Flex Mode: the capacity that can be matched is run in dual-channel, while the remainder runs in single-channel.

* Speed (e.g. PC5300). If speed is not the same, the lower speed of the two modules will be used. Likewise, the higher latency of the two modules will be used.

* Same CAS Latency (CL) or Column Address Strobe) latency, or CL.

* Number of chips and sides (e.g. two sides with four chips on each side).

* Matching sizeSize of rows and columns.

Dual-channel architecture is a technology implemented on motherboards by the motherboard manufacturer and does not apply to memory modules. Theoretically any matched pair of memory modules may be used in either single- or dual-channel operation, provided the motherboard supports this architecture.

With the introduction of [[DDR5]], each DDR5 DIMM has two independent sub-channels.

=== Performance ===

Theoretically, dual-channel configurations double the memory bandwidth when compared to single-channel configurations. This should not be confused with [[double data rate]] (DDR) memory, which doubles the usage of DRAM bus by transferring data both on the rising and falling edges of the memory bus clock signals.

A benchmark performed by [[TweakTown]], using SiSoftware Sandra, measured around 70% increase in performance of a quadruple-channel configuration, when compared to a dual-channel configuration.<ref name="tweaktown-banchmark">{{cite web

| url = http://www.tweaktown.com/articles/4416/intel_x79_quad_channel_and_z68_dual_channel_memory_performance_analysis/index.html

| title = Intel X79 Quad Channel and Z68 Dual Channel Memory Performance Analysis

| date = 2011-11-16 | access-date = 2013-11-30

| author = Shawn Baker | publisher = [[TweakTown]]

}}</ref>{{rp|p. 5}} Other tests performed by TweakTown on the same subject showed no significant differences in performance, leading to a conclusion that not all benchmark software is up to the task of exploiting increased parallelism offered by the multi-channel memory configurations.<ref name="tweaktown-banchmark" />{{rp|p. 6}}

=== {{Anchor|GANGED}}Ganged versus unganged ===

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When operating in triple-channel mode, [[memory latency]] is reduced due to interleaving, meaning that each module is accessed sequentially for smaller bits of data rather than completely filling up one module before accessing the next one. Data is spread amongst the modules in an alternating pattern, potentially tripling available memory bandwidth for the same amount of data, as opposed to storing it all on one module.

The architecture can only be used when all three, or a multiple of three, memory modules are identical in capacity and speed, and are placed in three-channel slots. When two memory modules are installed, the architecture will operate in dual-channel architecture mode.<ref name="support.intel.com">{{Citation|title=Desktop Boards – Triple Memory Modules|url=http://support.intel.com/support/motherboards/desktop/sb/CS-011965.htm#triple|publisher=Intel|access-date=2011-10-01|archive-date=2009-03-08|archive-url=https://web.archive.org/web/20090308093852/http://support.intel.com/support/motherboards/desktop/sb/CS-011965.htm#triple|url-status=dead}}, [https://www.intel.com/content/www/us/en/support/articles/000005657/boards-and-kits.html Single- and Multichannel Memory Modes]</ref>

=== Supporting processors ===

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The architecture can be used only when all four memory modules (or a multiple of four) are identical in capacity and speed, and are placed in quad-channel slots. When two memory modules are installed, the architecture will operate in a dual-channel mode; When three memory modules are installed, the architecture will operate in a triple-channel mode.<ref name="support.intel.com" />

=== Performance ===

A benchmark performed by [[TweakTown]], using SiSoftware Sandra, measured around 70% increase in performance of a quadruple-channel configuration, when compared to a dual-channel configuration.<ref name="tweaktown-banchmark">{{cite web

| url = http://www.tweaktown.com/articles/4416/intel_x79_quad_channel_and_z68_dual_channel_memory_performance_analysis/index.html

| title = Intel X79 Quad Channel and Z68 Dual Channel Memory Performance Analysis

| date = 2011-11-16 | access-date = 2013-11-30

| author = Shawn Baker | publisher = [[TweakTown]]

}}</ref>{{rp|p. 5}} Other tests performed by TweakTown on the same subject showed no significant differences in performance, leading to a conclusion that not all benchmark software is up to the task of exploiting increased parallelism offered by the multi-channel memory configurations.<ref name="tweaktown-banchmark" />{{rp|p. 6}}

=== Supporting processors ===

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== Octa-channel architecture ==

[[File:HP Z6 (极客湾Geekerwan) 029.png|thumb|alt=The image shows 4 RAM slots on the left and 4 on the right. The image center shows the socket and the AMD Ryzen Threadripper Pro 7995WX|Octa-channel setup with an AMD Ryzen Threadripper Pro 7995WX]]

Supported by [[Cavium#ThunderX2_SoCs|Cavium ThunderX2]] server processors, AMD's server processors from their [[Epyc]] platform, and the [[Threadripper|Threadripper PRO]] lineup of professional-class workstation processors from AMD Ryzen PRO product family.<ref>{{cite news|last1=Cutress|first1=Ian|title=AMD Prepares 32-Core Naples CPUs for 1P and 2P Servers: Coming in Q2|url=http://www.anandtech.com/show/11183/amd-prepares-32-core-naples-cpus-for-1p-and-2p-servers-coming-in-q2|archive-url=https://web.archive.org/web/20170307171613/http://www.anandtech.com/show/11183/amd-prepares-32-core-naples-cpus-for-1p-and-2p-servers-coming-in-q2|url-status=dead|archive-date=March 7, 2017|access-date=7 March 2017|publisher=Anandtech|date=7 March 2017}}</ref><ref>{{cite news|last1=Kennedy|first1=Patrick|title=Cavium ThunderX2 and OCP Platform Details|url=https://www.servethehome.com/cavium-thunderx2-ocp-platform-details/|access-date=14 November 2017|publisher=Serve the Home|date=9 November 2017}}</ref><ref>{{Cite web|last=Cutress|first=Ian|date=July 14, 2021|title=AMD Threadripper Pro Review: An Upgrade Over Regular Threadripper?|url=https://www.anandtech.com/show/16805/amd-threadripper-pro-review-an-upgrade-over-regular-threadripper|archive-url=https://web.archive.org/web/20210714131815/https://www.anandtech.com/show/16805/amd-threadripper-pro-review-an-upgrade-over-regular-threadripper|url-status=livedead|archive-date=July 14, 2021|access-date=August 18, 2021|website=[[AnandTech]]}}</ref>

== Dodeca-channel architecture ==

Supported by [[Cavium#ThunderX2_SoCs|Cavium ThunderX2]] server processors, AMD's server processors from their [[Epyc]] platform, and the [[Threadripper|Threadripper PRO]] lineup of professional-class workstation processors from AMD Ryzen PRO product family.<ref>{{cite news|last1=Cutress|first1=Ian|title=AMD Prepares 32-Core Naples CPUs for 1P and 2P Servers: Coming in Q2|url=http://www.anandtech.com/show/11183/amd-prepares-32-core-naples-cpus-for-1p-and-2p-servers-coming-in-q2|access-date=7 March 2017|publisher=Anandtech|date=7 March 2017}}</ref><ref>{{cite news|last1=Kennedy|first1=Patrick|title=Cavium ThunderX2 and OCP Platform Details|url=https://www.servethehome.com/cavium-thunderx2-ocp-platform-details/|access-date=14 November 2017|publisher=Serve the Home|date=9 November 2017}}</ref><ref>{{Cite web|last=Cutress|first=Ian|date=July 14, 2021|title=AMD Threadripper Pro Review: An Upgrade Over Regular Threadripper?|url=https://www.anandtech.com/show/16805/amd-threadripper-pro-review-an-upgrade-over-regular-threadripper|url-status=live|access-date=August 18, 2021|website=[[AnandTech]]}}</ref>

[[File:AMD Epyc 9754 in Dual-CPU-Socket-Serversystem (极客湾Geekerwan) 07.png|thumb|Server system containing two AMD Epyc CPUs with one dodeca-channel per CPU (768 GiB RAM in total)]]

Dodeca-channel or 12-channel memory architecture is introduced with AMD's server processors from their [[Epyc#Fourth generation Epyc (Genoa, Bergamo and Siena)|Epyc 9004]] platform released in 2022, using [[DDR5]] memory.<ref>{{Cite web |last=Goetting |first=Chris |date=2022-11-10 |title=AMD 4th Gen EPYC 9004 Series Launched: Genoa Tested In A Data Center Benchmark Gauntlet |url=https://hothardware.com/reviews/amd-genoa-data-center-cpu-launch |access-date=2023-12-07 |website=HotHardware |language=en-us}}</ref>

== See also ==

* [[List of deviceinterface bandwidthsbit rates]]

* [[Lockstep (computing)]]

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[[de:Dual Channel]]

[[de:Triple Channel]]

[[es:Arquitectura de memoria multicanal]]

[[es:Doble canal]]

[[it:Dual channel]]

[[ja:デュアルチャネル]]