A 200-pin PC6400 DDR2 SO-DIMM
A 204-pin PC3-10600 DDR3 SO-DIMM
A comparison between 200-pin DDR and DDR2 SDRAM SO-DIMMs, and a 204-pin DDR3 DIMM module[1]
A SO-DIMM slot on a computer motherboard

A SO-DIMM, SODIMM, or small outline dual in-line memory module, is a type of computer memory built using integrated circuits. SO-DIMMs are a smaller alternative to a DIMM, being roughly half the size of regular DIMMs.

SO-DIMMs are often used in systems that have limited space, which include notebooks, small-footprint personal computers such as those based on Mini-ITX motherboards, high-end upgradable office printers, and networking hardware such as routers and NAS devices.[2]

Visual identification

Most types of SO-DIMMs can be recognized at a glance by the distinctive notches that “key” them for different applications:[1]

Variants of 200-pin SO-DIMMs

The 200-pin SO-DIMM can be of the types DDR and DDR2. In both cases the notch is located at one fifth of the board length (20 pins + notch + 80 pins), but in DDR2 the notch is located slightly closer to the center of the board. These two types of memory are not interchangeable. The different notch locations are designed to prevent cross-installation, aiding at the same time in visually identifying 200-pin SO-DIMM modules.[1]

This variance is designed to prevent coupling of memory and controllers of different DDR generations due to electrical incompatibility. DDR SO-DIMMs operate at 2.5 V while DDR2 SO-DIMMs operate at 1.8 V.[10]

General characteristics

200- and 204-pin SO-DIMMs are 67.6 mm (2.66 inches) long and 31.75 mm (1.250 inches) wide, with a maximum total depth of 3.8 mm (0.15 inches).[11]

SO-DIMMs are more or less equal in power and voltage rating to DIMMs, and despite the smaller size of memory modules, SO-DIMM technology does not mandate lower performance compared to larger DIMMs. For example, DDR3 SO-DIMMs provide clock speeds such as 533 MHz (1066 MT/s, PC3-8500), CAS latencies such as 7, and higher capacities such as 4 GB per module.[12]

DDR2 SO-DIMM memory modules commonly have clock speeds from 200 MHz up to 400 MHz (PC2-6400). 204-pin SO-DIMMs can also contain DDR3 SDRAM, with specifications such as PC3-6400, PC3-8500, PC3-10600, PC3-14900 and PC3-17000.[13] 260-pin UniDIMMs may contain either DDR3 or DDR4 SDRAM, depending on their configuration. Some SO-DIMMs also provide ECC functionality; unbuffered ECC SO-DIMMs are called SO-CDIMMs.[14]

LowHal SODIMMs are made using a low-halogen, environmentally-friendly process,[15] which does not affect chip performance.

See also


  1. 1 2 3 "Are DDR, DDR2 and DDR3 SO-DIMM memory modules interchangeable?". Retrieved 2015-06-26.
  2. Synology Inc. "Synology RAM Module".
  3. "RAMCHECK 100-Pin DDR Adapter, a tool for testing and identifying JEDEC-compliant 100-pin DDR SO-DIMM modules". 2013. Retrieved 2015-06-26.
  4. "Small-outline SDRAM module (MT16LSDF3264(L)H 256 MB and MT16LSDF6464(L)H 512 MB) Datasheet" (PDF). Micron Technology. 2006-05-03. p. 22. Retrieved 2015-06-26.
  5. "DDR DIMM & SODIMM Modules (184-pin DDR DIMM, 100-pin DDR DIMM, and 200-pin DDR SO-DIMM modules)" (PDF). 2011. p. 4. Retrieved 2015-06-26.
  6. "NT2GC64B(C)H4B0PS / NT4GC64B(C)88B0(1)NS / NT8GC64B(C)8HB0NS PC3(L)-10600 / PC3(L)-12800 Unbuffered DDR3 SO-DIMM" (PDF). December 2012. p. 23. Retrieved 2015-06-26.
  7. "DDR4 SDRAM SO-DIMM (MTA18ASF1G72HZ, 8 GB) Datasheet" (PDF). Micron Technology. 2014-09-10. p. 18. Archived from the original (PDF) on 2014-11-29. Retrieved 2015-06-26.
  8. Geof Findley; Becky Loop (2014-09-16). "DDR4: The Right Memory for Your Next Server and High-End Desktop System" (PDF). Intel. p. 28. Retrieved 2015-06-26.
  9. "How Intel Plans to Transition Between DDR3 and DDR4 for the Mainstream". 2014-09-14. Retrieved 2015-06-26.
  10. "DRAM – Can I mix DDR, DDR2 and DDR3 modules-my PC?". Retrieved 2015-06-26.
  12. "Corsair Memory — 4GB DDR3 SODIMM Memory (CM3X4GSD1066)". Retrieved 1 October 2015.
  13. "204-Pin DDR3 SDRAM Unbuffered SODIMM Design Specification".
  14. "Define-SO-CDIMM". RAMpedia. Retrieved 2014-08-24.
  15. "Low-Halogen RAM? - Lenovo Community". 2009-10-17. Retrieved 2014-08-24.
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