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An 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, such as notebooks, small-footprint personal computers (such as those with a Mini-ITX motherboard), high-end upgradable office printers, and networking hardware like routers and NAS devices.

Visual identification

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

• 100-pin SO-DIMMs have two notches.
• 144-pin SO-DIMMs have a single notch near the center.
• 200-pin SO-DIMMs have a single notch nearer to one side. The exact location of this notch varies (read below).
• 204-pin SO-DIMMs (DDR3) have a single notch closer to the center than on 200-pin SO-DIMMs.
• 260-pin SO-DIMMs (DDR4), 69.6 mm (2.74 inches) wide and 30 mm (1.2 inches) high, making them 2 mm (0.079 inches) wider than DDR3 SO-DIMMs, with a single notch after pin 144.
• 260-pin SO-DIMMs (UniDIMM), 69.6 mm (2.74 inches) wide and 30 mm (1.2 inches) or 20 mm (0.79 inches) high, with a single notch placed differently than on DDR3 SO-DIMMs.

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. Keep this in mind when attempting to visually identify 200-pin SO-DIMM modules.

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 Volts while DDR2 SO-DIMMs operate at 1.8 Volts.

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).

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, SO-DIMMs provide clock speeds such as 400 MHz (PC-3200), CAS latencies such as 2, 2.5 and 3, and higher capacities such as 512 MB or 1 GB.

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, and PC3-12800. 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.

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

See also

• Dual in-line package (DIP)
• Memory scrambling
• Memory geometry – logical configuration of RAM modules (channels, ranks, banks, etc.)
• Rambus in-line memory module (RIMM)
• Single in-line memory module (SIMM)
• Single in-line package (SIP)
• Zig-zag in-line package (ZIP)

References

1. ^ "Are DDR, DDR2 and DDR3 SO-DIMM memory modules interchangeable?". acer.custhelp.com. Retrieved 2015-06-26.
2. Synology Inc. "Synology RAM Module". synology.com.
3. "RAMCHECK 100-Pin DDR Adapter, a tool for testing and identifying JEDEC-compliant 100-pin DDR SO-DIMM modules". memorytesters.com. 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 & SO-DIMM Modules (184-pin DDR DIMM, 100-pin DDR DIMM, and 200-pin DDR SO-DIMM modules)" (PDF). smartm.com. 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). nanya.com. 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.activeevents.com. Intel. p. 28. Retrieved 2015-06-26.
9. "How Intel Plans to Transition Between DDR3 and DDR4 for the Mainstream". techpowerup.com. 2014-09-14. Retrieved 2015-06-26.
10. micron.com - 200 Pin, PC2700 DDR SDRAM Unbuffered SO–DIMM REFERENCE DESIGN SPECIFICATION page 26
11. webcitation.org/5kFxvjQmo
12. "Define-SO-CDIMM". RAMpedia. Retrieved 2014-08-24.
13. "Low-Halogen RAM? - Lenovo Community". Forums.lenovo.com. 2009-10-17. Retrieved 2014-08-24.

External links

• How to Install PC Memory Guides
• Ruggedizing RAM for industrial systems (XR-DIMM form factor)

• Computer memory form factor