Editing DIMM

{{Short description|Computer memory module}}
[[File:168 pin and 184 pin DIMM.jpg|thumb|Two types of DIMMs: a 168-pin [[SDRAM]] module (top) and a 184-pin [[DDR SDRAM]] module (bottom). The SDRAM module has two notches (rectangular cuts or incisions) on the bottom edge, while the DDR1 SDRAM module has one. Also, each module has eight RAM chips, but the lower one has an unoccupied space for the ninth chip; this space is occupied in [[ECC_memory|ECC]] DIMMs.]]
[[File:Abit-BP6 (cropped) SDRAM DIMM slots.JPG|thumb|upright=1.6|Three [[SDRAM]] DIMM slots on a [[ABIT BP6]] computer motherboard.]]

A '''DIMM''' ('''Dual In-line Memory Module''') is a popular type of [[memory module]] used in computers. It is a [[printed circuit board]] with one or both sides (front and back) holding [[DRAM]] [[integrated circuit|chip]]s and [[Pin (electronics)|pin]]s.<ref name="GeeksforGeeks 2020 e240">{{cite web | title=What is DIMM(Dual Inline Memory Module)? | website=GeeksforGeeks | date=2020-04-15 | url=https://www.geeksforgeeks.org/what-is-dimmdual-inline-memory-module/ | access-date=2024-04-07 | quote=In the case of SIMM, the connectors are only present on the single side of the module...DIMM has a row of connectors on both sides(front and back) of the module | archive-date=2024-04-07 | archive-url=https://web.archive.org/web/20240407102508/https://www.geeksforgeeks.org/what-is-dimmdual-inline-memory-module/ | url-status=live }}</ref> The vast majority of DIMMs are manufactured in compliance with [[JEDEC memory standards]], although there are proprietary DIMMs. DIMMs come in a variety of speeds and capacities, and are generally one of two lengths: PC, which are {{Convert|133.35|mm|in|2|abbr=on}}, and laptop (SO-DIMM), which are about half the length at {{Convert|67.60|mm|in|2|abbr=on}}.<ref name=":0" />

== History ==
DIMMs (Dual In-line Memory Module) were a 1990s upgrade for [[SIMM]]s (Single In-line Memory Modules)<ref>{{cite book | url=https://books.google.com/books?id=zWrZY1OgTPsC&dq=dimm+simm+ram&pg=PA576 | title=The X86 Microprocessors: Architecture and Programming (8086 to Pentium) | isbn=9788131732465 | last1=Lyla | first1=Das B. | date=September 2010 | publisher=Pearson Education India }}</ref><ref>{{Cite book|url=https://books.google.com/books?id=gXaRdKyD4PsC&dq=so+dimm+1995&pg=PA334|title=Upgrading and Repairing PCs: Upgrading and Repairing_c21|first=Scott|last=Mueller|date=March 7, 2013|publisher=Que Publishing|isbn=9780133105360|via=Google Books|access-date=December 26, 2023|archive-date=September 17, 2024|archive-url=https://web.archive.org/web/20240917213349/https://books.google.com/books?id=gXaRdKyD4PsC&dq=so+dimm+1995&pg=PA334#v=onepage&q=so%20dimm%201995&f=false|url-status=live}}</ref> as [[Intel]] [[P5 (microarchitecture)|P5]]-based [[Pentium]] processors began to gain market share. The Pentium had a 64-bit [[bus (computing)|bus]] width, which would require SIMMs installed in matched pairs in order to populate the data bus. The processor would then access the two SIMMs in parallel.

DIMMs were introduced to eliminate this disadvantage. The contacts on SIMMs on both sides are redundant, while DIMMs have separate electrical contacts on each side of the module.<ref>{{cite book | url=https://books.google.com/books?id=SrP3aWed-esC | title=Memory Systems: Cache, DRAM, Disk | isbn=9780080553849 | last1=Jacob | first1=Bruce | last2=Wang | first2=David | last3=Ng | first3=Spencer | date=28 July 2010 | publisher=Morgan Kaufmann }}</ref> This allowed them to double the SIMMs 32-bit data path into a 64-bit data path.<ref name="auto1">{{cite book | url=https://books.google.com/books?id=E1p2FDL7P5QC&dq=simm+32+bits+dimm+64+bits&pg=PA442 | title=Upgrading and Repairing PCS | isbn=9780789729743 | last1=Mueller | first1=Scott | date=2004 | publisher=Que | access-date=2023-12-26 | archive-date=2024-09-17 | archive-url=https://web.archive.org/web/20240917213304/https://books.google.com/books?id=E1p2FDL7P5QC&dq=simm+32+bits+dimm+64+bits&pg=PA442#v=onepage&q=simm%2032%20bits%20dimm%2064%20bits&f=false | url-status=live }}</ref>

The name "DIMM" was chosen as an acronym for ''Dual In-line Memory Module'' symbolizing the split in the contacts of a SIMM into two independent rows.<ref name="auto1"/> Many enhancements have occurred to the modules in the intervening years, but the word "DIMM" has remained as one of the generic terms{{clarify|date=March 2025}} for a computer memory module.

== Variants ==
[[File:THL32V1055BTG-6.jpg|thumb|72-pin SO-DIMM]]
There are numerous DIMM variants, employing different pin-counts:

;DIMM
:* 100-pin: printer [[SDRAM]] and printer [[ROM]] (e.g., [[PostScript]])
:* 168-pin: [[SDR SDRAM]], sometimes used for FPM/EDO DRAM in workstations or servers, may be 3.3 or 5 V
:* 184-pin: [[DDR SDRAM]]
:* 200-pin: [[Fast page mode|FPM]]/[[EDO DRAM]] in some [[Sun Microsystems|Sun]] workstations and servers
:* 240-pin: [[DDR2 SDRAM]], [[DDR3 SDRAM]] and [[FB-DIMM]] DRAM
:* 278-pin: [[Hewlett-Packard|HP]] high density SDRAM
:* 288-pin: [[DDR4 SDRAM]] and [[DDR5 SDRAM]]<ref name="anandtech-ddr5">{{cite web|url=https://www.anandtech.com/show/15912/ddr5-specification-released-setting-the-stage-for-ddr56400-and-beyond|title=DDR5 Memory Specification Released: Setting the Stage for DDR5-6400 And Beyond|last=Smith|first=Ryan|date=2020-07-14|website=AnandTech|access-date=2020-07-15|archive-date=2021-04-05|archive-url=https://web.archive.org/web/20210405133714/https://www.anandtech.com/show/15912/ddr5-specification-released-setting-the-stage-for-ddr56400-and-beyond|url-status=live}}</ref>
;SO-DIMM
:* {{0}}72-pin: FPM DRAM and EDO DRAM;<ref name="auto">{{cite book | url=https://books.google.com/books?id=xCXVGneKwScC | title=Upgrading and Repairing Laptops | isbn=9780789728005 | last1=Mueller | first1=Scott | date=2004 | publisher=Que | access-date=2023-12-26 | archive-date=2024-09-17 | archive-url=https://web.archive.org/web/20240917213427/https://books.google.com/books?id=xCXVGneKwScC | url-status=live }}</ref> different pin configuration from 72-pin SIMM
:* 144-pin: SDR SDRAM,<ref name="auto"/> sometimes used for [[DDR2 SDRAM]]
:* 200-pin: DDR SDRAM<ref name="auto"/> and DDR2 SDRAM
:* 204-pin: DDR3 SDRAM
:* 260-pin: DDR4 SDRAM
:* 260-pin: [[UniDIMM]]s carrying either DDR3 or DDR4 SDRAM; differently notched than DDR4 SO-DIMMs
:* 262-pin: [[DDR5 SDRAM]]
;MiniDIMM
:* 244-pin: DDR2 SDRAM
[[File:Nanonote 03 2.jpg|thumb|256&nbsp;MB MicroDIMM PC133 SDRAM (double sided, 4 chips).]]
;MicroDIMM
:* 144-pin: SDRAM<ref name="auto"/>
:* 172-pin: DDR SDRAM<ref name="auto"/>
:* 214-pin: DDR2 SDRAM

== SO-DIMM ==
[[File:Assorted SO-DIMM Modules.jpg|thumb|Assorted SO-DIMM Modules]]
[[File:Samsung-1GB-DDR2-Laptop-RAM.jpg|thumb|A 200-pin [[PC2-5300]] DDR2 SO-DIMM.]]
[[File:4GB_DDR3_SO-DIMM.jpg|thumb|A 204-pin PC3-10600 DDR3 SO-DIMM.]]
[[File:DDR_SO-DIMM_slot_PNr°0341.jpg|thumb|upright=1.6|A SO-DIMM slot on a computer [[motherboard]].]]

A '''SO-DIMM''' (pronounced "so dim" {{IPAc-en|ˈ|s|oʊ|d|ɪ|m}}, also spelled '''SODIMM''') or '''small outline DIMM''', is a smaller alternative to a DIMM, being roughly half the physical size of a regular DIMM. The first SO-DIMMs had 72 pins and were introduced by JEDEC in 1997.<ref name="auto"/><ref>{{cite web | url=https://www.jedec.org/standards-documents/docs/module-444 | title=72 Pin DRAM SO-DIMM &#124; JEDEC | access-date=2023-11-09 | archive-date=2024-09-17 | archive-url=https://web.archive.org/web/20240917213306/https://www.jedec.org/standards-documents/docs/module-444 | url-status=live }}</ref><ref>{{Cite web|url=http://archive.org/details/completeidiotsgu00fult|title=The complete idiot's guide to upgrading and repairing PCs|first=Jennifer|last=Fulton|date=November 9, 2000|publisher=Indianapolis, IN : Alpha Books|via=Internet Archive}}</ref> Before its introduction, many laptops would use proprietary<ref>{{Cite web|url=https://books.google.com/books?id=u2cfcECC1dwC&dq=%2260-pin%22+memory+card&pg=PP36|title=PC Magazine|last1=Jones|first1=Mitt|date=December 25, 1990|publisher=Ziff-Davis Publishing Company|via=Google Books|access-date=February 4, 2024|archive-date=September 17, 2024|archive-url=https://web.archive.org/web/20240917213428/https://books.google.com/books?id=u2cfcECC1dwC&dq=%2260-pin%22+memory+card&pg=PP36#v=onepage&q=%2260-pin%22%20memory%20card&f=false|url-status=live}}</ref> RAM modules which were expensive and hard to find.<ref name="auto"/><ref>{{cite book | url=https://books.google.com/books?id=O0FTac_k7CIC&dq=laptop+proprietary+sodimm&pg=PA36 | title=Peter Norton's New Inside the PC | isbn=9780672322891 | last1=Norton | first1=Peter | last2=Clark | first2=Scott H. | date=2002 | publisher=Sams }}</ref>

SO-DIMMs are often used in computers that have limited space, which include [[laptop]]s, [[notebook computer]]s, small-footprint personal computers such as those based on [[Nano-ITX motherboard]]s, high-end upgradable office [[Computer printer|printers]], and [[networking hardware]] such as [[Router (computing)|routers]] and [[Network-attached storage|NAS]] devices.<ref>{{cite web |author=Synology Inc. |title=Synology RAM Module |url=https://www.synology.com/en-global/products/Synology_RAM_Module |work=synology.com |access-date=2022-03-23 |archive-date=2016-06-02 |archive-url=https://web.archive.org/web/20160602224830/https://www.synology.com/en-global/products/Synology_RAM_Module |url-status=live }}</ref> They are usually available with the same size data path and speed ratings of the regular DIMMs though normally with smaller capacities.

== SDR 168-pin SDRAM ==
[[File:Notch position between DDR and DDR2.jpg|thumb|right|upright=1.6|Notch positions on DDR (top) and DDR2 (bottom) DIMM modules.]]

On the bottom edge of 168-pin DIMMs there are two notches, and the location of each notch determines a particular feature of the module. The first notch is the DRAM key position, which represents RFU (reserved future use), [[Registered memory|registered]], and [[Unbuffered memory|unbuffered]] DIMM types (left, middle and right position, respectively). The second notch is the voltage key position, which represents 5.0&nbsp;V, 3.3&nbsp;V, and RFU DIMM types (order is the same as above).

== DDR DIMMs ==
[[File:16 GiB-DDR4-RAM-Riegel RAM019FIX Small Crop 90 PCNT.png|thumb|upright=1.6|16&nbsp;GiB DDR4-2666 1.2&nbsp;V [[UDIMM|Unbuffered DIMM (UDIMM)]].]]

[[DDR SDRAM|DDR]], [[DDR2 SDRAM|DDR2]], [[DDR3]], [[DDR4]] and [[DDR5]] all have different pin counts and/or different notch positions, and none of them are [[forward compatible]] or [[backward compatible]]. DDR5 SDRAM is the most recent type of DDR memory and has been in use since 2020.

== SPD EEPROM ==
A DIMM's capacity and other operational parameters may be identified with [[serial presence detect]] (SPD), an additional chip which contains information about the module type and timing for the memory controller to be configured correctly. The SPD [[EEPROM]] connects to the [[System Management Bus]] and may also contain thermal sensors (''TS-on-DIMM'').<ref>{{Cite web |url=http://www.tempsensornews.com/generic-temp-sensors/temperature-sensor-in-dimm-memory-modules/ |title=Temperature Sensor in DIMM memory modules |access-date=2013-03-17 |archive-date=2016-04-01 |archive-url=https://web.archive.org/web/20160401094930/http://www.tempsensornews.com/generic-temp-sensors/temperature-sensor-in-dimm-memory-modules/ |url-status=usurped }}</ref>

== Error correction ==
[[ECC memory|ECC]] DIMMs are those that have extra data bits which can be used by the system memory controller to detect and correct errors. There are numerous ECC schemes, but perhaps the most common is Single Error Correct, Double Error Detect ([[SECDED]]) which uses an extra byte per 64-bit word. ECC modules usually carry a multiple of 9 instead of a multiple of 8 chips.

== Ranking ==
{{main|Memory rank}}
Sometimes memory modules are designed with two or more independent sets of DRAM chips connected to the same address and data buses; each such set is called a '''rank'''. Ranks that share the same slot, only one rank may be accessed at any given time; it is specified by activating the corresponding rank's chip select (CS) signal. The other ranks on the module are deactivated for the duration of the operation by having their corresponding CS signals deactivated. DIMMs are currently being commonly manufactured with up to four ranks per module. Consumer DIMM vendors have recently begun to distinguish between single and dual ranked DIMMs.

After a memory word is fetched, the memory is typically inaccessible for an extended period of time while the sense amplifiers are charged for access of the next cell. By interleaving the memory (e.g. cells 0, 4, 8, etc. are stored together in one rank), sequential memory accesses can be performed more rapidly because sense amplifiers have 3 cycles of idle time for recharging, between accesses.

DIMMs are often referred to as "single-sided" or "[[Double-sided RAM|double-sided]]" to describe whether the DRAM chips are located on one or both sides of the module's [[printed circuit board]] (PCB). However, these terms may cause confusion, as the physical layout of the chips does not necessarily relate to how they are logically organized or accessed.

[[JEDEC]] decided that the terms "dual-sided", "double-sided", or "dual-banked" were not correct when applied to [[registered DIMM]]s (RDIMMs).

== Organization ==
Most DIMMs are built using "×4" ("by four") or "×8" ("by eight") memory chips with up to nine chips per side; "×4" and "×8" refer to the data width of the DRAM chips in bits. High-capacity DIMMs such as 256&nbsp;GB DIMMs can have up to 19 chips per side.

In the case of "×4" registered DIMMs, the data width per side is 36 bits; therefore, the [[memory controller]] (which requires 72 bits) needs to address both sides at the same time to read or write the data it needs. In this case, the two-sided module is single-ranked. For "×8" registered DIMMs, each side is 72 bits wide, so the memory controller only addresses one side at a time (the two-sided module is dual-ranked).

The above example applies to ECC memory that stores 72 bits instead of the more common 64. There would also be one extra chip per group of eight, which is not counted.

== Speeds ==
For various technologies, there are certain bus and device clock frequencies that are standardized; there is also a decided nomenclature for each of these speeds for each type.

DIMMs based on Single Data Rate (SDR) DRAM have the same bus frequency for data, address and control lines. DIMMs based on [[Double Data Rate]] (DDR) DRAM have data but not the strobe at double the rate of the clock; this is achieved by clocking on both the rising and falling edge of the data strobes. Power consumption and voltage gradually became lower with each generation of DDR-based DIMMs.

Another influence is Column Access Strobe (CAS) latency, or CL, which affects memory access speed. This is the delay time between the READ command and the moment data is available. See main article [[CAS latency|CAS/CL]].

{{Col-float|width=50em}}
{{Table alignment}}
{| class="wikitable plainrowheaders defaultright col1left col2left" style="margin-right: 2em;"
|+ [[SDR SDRAM]] DIMMs
|-
! scope="col" | Chip
! scope="col" | Module
! scope="col" | [[Clock rate|Effective clock]]<br/>({{abbr|MHz|megaherz}})
! scope="col" | [[Transfer (computing)|Transfer rate]]<br/>([[Transfers per second|{{abbr|MT/s|megatransfers per second}}]])
! scope="col" | Voltage<br/>([[Volt|{{abbr|V|volt}}]])
|-
! scope="row" | SDR-66
| PC-66 || 66 || 66 || 3.3
|-
! scope="row" | SDR-100
| PC-100 || 100 || 100|| 3.3
|-
! scope="row" | SDR-133
| PC-133 || 133 || 133 || 3.3
|}

{{Table alignment}}
{| class="wikitable plainrowheaders defaultright col1left col2left" style="margin-right: 2em;"
|+ [[DDR SDRAM]] (DDR1) DIMMs
|-
! scope="col" | Chip
! scope="col" | Module
! scope="col" | Memory clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | I/O bus clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | [[Transfer (computing)|Transfer rate]]<br/>([[Transfers per second|{{abbr|MT/s|megatransfers per second}}]])
! scope="col" | Voltage<br/>([[Volt|{{abbr|V|volt}}]])
|-
! scope="row" | DDR-200
| PC-1600 || 100 || 100 || 200 || 2.5
|-
! scope="row" | DDR-266
| PC-2100 || 133 || 133 || 266 || 2.5
|-
! scope="row" | DDR-333
| PC-2700 || 166 || 166 || 333 || 2.5
|-
! scope="row" | DDR-400
| PC-3200 || 200 || 200 || 400 || 2.6
|}

{{Table alignment}}
{| class="wikitable plainrowheaders defaultright col1left col2left" style="margin-right: 2em;"
|+ [[DDR2 SDRAM]] DIMMs
|-
! scope="col" | Chip
! scope="col" | Module
! scope="col" | Memory clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | I/O bus clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | [[Transfer (computing)|Transfer rate]]<br/>([[Transfers per second|{{abbr|MT/s|megatransfers per second}}]])
! scope="col" | Voltage<br/>([[Volt|{{abbr|V|volt}}]])
|-
! scope="row" | DDR2-400
| PC2-3200 || 100 || 200 || 400 || 1.8
|-
! scope="row" | DDR2-533
| PC2-4200 || 133 || 266 || 533 || 1.8
|-
! scope="row" | DDR2-667
| PC2-5300 || 166 || 333 || 667 || 1.8
|-
! scope="row" | DDR2-800
| PC2-6400 || 200 || 400 || 800 || 1.8
|-
! scope="row" | {{nowrap|DDR2-1066}}
| {{nowrap|PC2-8500}} || 266 || 533 || 1066 || 1.8
|}

{{Col-float-break|width=60em}}

{{Table alignment}}
{| class="wikitable plainrowheaders defaultright col1left col2left"
|+ [[DDR3 SDRAM]] DIMMs
|-
! scope="col" | Chip
! scope="col" | Module
! scope="col" | Memory clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | I/O bus clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | [[Transfer (computing)|Transfer rate]]<br/>([[Transfers per second|{{abbr|MT/s|megatransfers per second}}]])
! scope="col" | Voltage<br/>([[Volt|{{abbr|V|volt}}]])
|-
! scope="row" | DDR3-800
| PC3-6400 || 100 || 400 || 800 || 1.5
|-
! scope="row" | DDR3-1066
| PC3-8500 || 133 || 533 || 1066 || 1.5
|-
! scope="row" | DDR3-1333
| PC3-10600 || 166 || 667 || 1333 || 1.5
|-
! scope="row" | DDR3-1600
| PC3-12800 || 200 || 800 || 1600 || 1.5
|-
! scope="row" | DDR3-1866
| PC3-14900 || 233 || 933 || 1866 || 1.5
|-
! scope="row" | DDR3-2133
| PC3-17000 || 266 || 1066 || 2133 || 1.5
|-
! scope="row" | DDR3-2400
| PC3-19200 || 300 || 1200 || 2400 || 1.5
|}

{{Table alignment}}
{| class="wikitable plainrowheaders defaultright col1left col2left" style="margin-right: 2em;"
|+ [[DDR4 SDRAM]] DIMMs
|-
! scope="col" | Chip
! scope="col" | Module
! scope="col" | Memory clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | I/O bus clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | [[Transfer (computing)|Transfer rate]]<br/>([[Transfers per second|{{abbr|MT/s|megatransfers per second}}]])
! scope="col" | Voltage<br/>([[Volt|{{abbr|V|volt}}]])
|-
! scope="row" | DDR4-1600
| PC4-12800 || 200 || 800 || 1600 || 1.2
|-
! scope="row" | DDR4-1866
| PC4-14900 || 233 || 933 || 1866 || 1.2
|-
! scope="row" | DDR4-2133
| PC4-17000 || 266 || 1066 || 2133 || 1.2
|-
! scope="row" | DDR4-2400
| PC4-19200 || 300 || 1200 || 2400 || 1.2
|-
! scope="row" | DDR4-2666
| PC4-21300 || 333 || 1333 || 2666 || 1.2
|-
! scope="row" | DDR4-3200
| PC4-25600 || 400 || 1600 || 3200 || 1.2
|}

{{Table alignment}}
{| class="wikitable plainrowheaders defaultright col1left col2left" style="margin-right: 2em;"
|+ [[DDR5 SDRAM]] DIMMs
|-
! scope="col" | Chip
! scope="col" | Module
! scope="col" | Memory clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | I/O bus clock<br/>({{abbr|MHz|megaherz}})
! scope="col" | [[Transfer (computing)|Transfer rate]]<br/>([[Transfers per second|{{abbr|MT/s|megatransfers per second}}]])
! scope="col" | Voltage<br/>([[Volt|{{abbr|V|volt}}]])
|-
! scope="row" | DDR5-4000
| PC5-32000 || 2000 || 2000 || 4000 || 1.1
|-
! scope="row" | DDR5-4400
| PC5-35200 || 2200 || 2200 || 4400 || 1.1
|-
! scope="row" | DDR5-4800
| PC5-38400 || 2400 || 2400 || 4800 || 1.1
|-
! scope="row" | DDR5-5200
| PC5-41600 || 2600 || 2600 || 5200 || 1.1
|-
! scope="row" | DDR5-5600
| PC5-44800 || 2800 || 2800 || 5600 || 1.1
|-
! scope="row" | DDR5-6000
| PC5-48000 || 3000 || 3000 || 6000 || 1.1
|-
! scope="row" | DDR5-6200
| PC5-49600 || 3100 || 3100 || 6200 || 1.1
|-
! scope="row" | DDR5-6400
| PC5-51200 || 3200 || 3200 || 6400 || 1.1
|-
! scope="row" | DDR5-6800
| PC5-54400 || 3400 || 3400 || 6800 || 1.1
|-
! scope="row" | DDR5-7200
| PC5-57600 || 3600 || 3600 || 7200 || 1.1
|-
! scope="row" | DDR5-7600
| PC5-60800 || 3800 || 3800 || 7600 || 1.1
|-
! scope="row" | DDR5-8000
| PC5-64000 || 4000 || 4000 || 8000 || 1.1
|-
! scope="row" | DDR5-8400
| PC5-67200 || 4200 || 4200 || 8400 || 1.1
|-
! scope="row" | DDR5-8800
| PC5-70400 || 4400 || 4400 || 8800 || 1.1
|}

{{Col-float-end}}

== Form factors ==
[[File:Laptop_SODIMM_DDR_Memory_Comparison_V2.svg|right|thumb|A comparison between 200-pin DDR and DDR2 SDRAM SO-DIMMs, and a 204-pin DDR3 SO-DIMM module.<ref name="custhelp">{{cite web
 | url = http://acer.custhelp.com/app/answers/detail/a_id/2178/~/are-ddr,-ddr2-and-ddr3-so-dimm-memory-modules-interchangeable%3F
 | title = Are DDR, DDR2 and DDR3 SO-DIMM memory modules interchangeable?
 | access-date = 2015-06-26
 | website = acer.custhelp.com
 }}{{Dead link|date=September 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>]]
Several form factors are commonly used in DIMMs. Single Data Rate Synchronous DRAM (SDR SDRAM) DIMMs were primarily manufactured in {{convert|1.5|in|mm}} and {{convert|1.7|in|mm}} heights. When [[rack unit|1U rackmount]] servers started becoming popular, these form factor registered DIMMs had to plug into angled DIMM sockets to fit in the {{convert|1.75|in|mm}} high box. To alleviate this issue, the next standards of DDR DIMMs were created with a "low profile" (LP) height of around {{convert|1.2|in|mm}}. These fit into vertical DIMM sockets for a 1U platform.

With the advent of [[blade server]]s, angled slots have once again become common in order to accommodate LP form factor DIMMs in these space-constrained boxes. This led to the development of the Very Low Profile (VLP) form factor DIMM with a height of around {{convert|0.72|in|mm}}. The DDR3 JEDEC standard for VLP DIMM height is around {{convert|0.740|in|mm}}. These will fit vertically in [[Advanced Telecommunications Computing Architecture|ATCA]] systems.

Full-height 240-pin DDR2 and DDR3 DIMMs are all specified at a height of around {{convert|1.18|in|mm}} by standards set by JEDEC. These form factors include 240-pin DIMM, SO-DIMM, Mini-DIMM and Micro-DIMM.<ref>[http://www.jedec.org/sites/default/files/docs/MO-269J.pdf JEDEC MO-269J Whitepaper.], accessed Aug. 20, 2014.</ref>

Full-height 288-pin DDR4 DIMMs are slightly taller than their DDR3 counterparts at {{convert|1.23|in|mm}}. Similarly, VLP DDR4 DIMMs are also marginally taller than their DDR3 equivalent at nearly {{convert|0.74|in|mm}}.<ref>[http://www.jedec.org/sites/default/files/docs/MO-309E.pdf JEDEC MO-309E Whitepaper.], accessed Aug. 20, 2014.</ref>

As of Q2 2017, Asus has had a [[PCI-E]] based "DIMM.2", which has a similar socket to DDR3 DIMMs and is used to put in a module to connect up to two [[M.2]] [[NVMe]] solid-state drives. However, it cannot use common DDR type ram and does not have much support other than Asus.<ref>[https://www.techpowerup.com/229448/asus-dimm-2-is-an-m-2-riser-card ASUS DIMM.2 is a M.2 Riser Card.] {{Webarchive|url=https://web.archive.org/web/20200605022413/https://www.techpowerup.com/229448/asus-dimm-2-is-an-m-2-riser-card |date=2020-06-05 }}, accessed Jun. 4, 2020.</ref>

Regular DIMMs are generally 133.35&nbsp;mm in length, while SO-DIMMs are generally 67.6&nbsp;mm in length.<ref name=":0">{{cite web |url=https://www.simmtester.com/News/PublicationArticle/168 |date=2009-10-06 |accessdate=2021-05-13 |title=Common DIMM Memory Form Factor |archive-date=2021-05-13 |archive-url=https://web.archive.org/web/20210513093518/https://www.simmtester.com/News/PublicationArticle/168 |url-status=live }}</ref>

== See also ==
{{Portal|Electronics}}

{{Div col|colwidth=25em}}
* [[Dual in-line package]] (DIP)
* [[Memory scrambling]]
* [[Memory geometry]]{{snd}} logical configuration of RAM modules (channels, ranks, banks, etc.)
* [[Motherboard]]
* [[NVDIMM]]{{snd}} non-volatile DIMM
* [[Row hammer]]
* [[Rambus in-line memory module]] (RIMM)
* [[Single in-line memory module]] (SIMM)
* [[Single in-line package]] (SIP)
* [[Zig-zag in-line package]] (ZIP)
* [[Compression Attached Memory Module]] (CAMM)
{{Div col end}}

== References ==
{{Reflist}}

== External links ==
{{Commons category|DIMM}}

* [http://www.oempcworld.com/support/How_to_Install_PC_Memory.htm How to Install PC Memory guides]
* [http://www.supertalent.com/datasheets/VLP_WHITEPAPER.pdf Very Low Profile (VLP) DDR2 Whitepaper (PDF)]
* [https://reviewpanther.com/is-4gb-ram-good-for-a-laptop/ Is 4GB RAM Good For a Laptop?]

{{DRAM}}

[[Category:Computer memory form factor]]