SO-DIMM

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PC2700 200-pin SO-DIMM

A SO-DIMM, or small outline dual in-line memory module, is a type of computer memory integrated circuit.

SO-DIMMs are a smaller alternative to a DIMM, being roughly half the size of regular DIMMs. As a result SO-DIMMs are mainly used in notebooks, small footprint PCs (such as those with a Mini-ITX motherboard), high-end upgradable office printers and networking hardware like routers.

SO-DIMMs have 72, 100, 144, or 200 pins. The 100 pin package supports 32-bit data transfer, while the 144 and 200 package supports 64-bit data transfer. This compares to regular DIMMs that have 168, 184, or 240 pins, all supporting 64-bit data transfer.

The different types of SO-DIMMs can be recognized at a glance by the distinctive notches used to "key" them for different applications: 100-pin SO-DIMMs have two notches, 144-pin SO-DIMMs have a single notch near (but not at) the center, and 200-pin SO-DIMMs have a single notch nearer to one side.

The 200-pin SO-DIMM has two variations for locating the notch that are nearly indistinguishable. If the notch is located further outboard, it indicates the DDR class of memory. When the notch is located towards the center of the board, it indicates DDR2. These two types of memory are not interchangeable and thus have slightly different notch locations that prevent cross installation. The PC2700 200-pin SO-DIMM depicted in the accompanying photograph shows a notch slightly outboard, and is thus DDR. Caution should be exercised when visually identifying 200-pin SO-DIMM modules.

SO-DIMMs are more or less equal in power and voltage to DIMMs, and as memory technology moves forward, both SO-DIMMs and DIMMs are available in equal speed (PC3200, for example, and clock speeds such as 2.0, 2.5 and 3.0 CAS latency) and capacity (512MB, 1GB, etc.).