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SO-DIMMs (also written SODIMMs) 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 PCs (such as those with a Mini-ITX motherboard), high-end upgradable office printers, and networking hardware like routers.
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.
- 256-pin SO-DIMMs (DDR4).
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.
200- and 204-pin SO-DIMMs measure at 6.76 cm in length and a width of 3.175 cm with a maximum total depth of 0.38 cm.
SO-DIMMs are more or less equal in power and voltage rating to DIMMs, and as memory technology moves forward and despite their smaller size, SO-DIMM technology allows for performance speeds as high as the those of the larger DIMMs[clarification needed] (clock speeds such as 400 MHz PC-3200, for example, and CAS latency such as 2.0, 2.5, and 3.0) and capacity (512MB, 1GB, etc.).
DDR2 SO-DIMM memory modules commonly have clock speeds from 200 MHz up to 800 MHz PC2-6400. The latest 204-pin SO-DIMMs can contain DDR3 SDRAM, with specifications such as PC3-6400, PC3-8500, PC3-10600, and PC3-12800.
LowHal SODIMMs are made using a low-halogen, environmentally-friendly process. It does not affect chip performance.
- micron.com - 200 Pin, PC2700 DDR SDRAM Unbuffered SO–DIMM REFERENCE DESIGN SPECIFICATION page 26
- "Low-Halogen RAM? - Lenovo Community". Forums.lenovo.com. 2009-10-17. Retrieved 2014-08-24.
- "Define-SO-CDIMM". RAMpedia. Retrieved 2014-08-24.
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