Editing DIMM (section)

== 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>