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A single in-line memory module (SIMM) is a small circuit board or substrate, typically about 10 x 2cm, with RAM integrated circuits or die on one or both sides and a single row of pins along one long edge.


SIMMs are typically installed in groups, with their substrates at right-angles to the main circuit board (the motherboard). This configuration allows greater packing density than direct mounting of dual in-line packages (DIPs) of RAM on the motherboard. In 1993, one SIMM typically held one or four megabytes. By early 1997, one could hold 8, 16, or 32 MB.[1] These have since been superseded by dual in-line memory modules (DIMMs).[2]


The Macintosh Plus, introduced in January 1986, was the first model from Apple Computer to feature SIMM slots for memory upgrades.[3] Starting with the Power Macintosh 9500 in June 1995, Apple began switching to DIMM slots for memory upgrades.[4]


  1. Single In-line Memory Module at the Free On-Line Dictionary Of Computing. 1997-01-05.
  2. Dual In-line Memory Module at the Free On-Line Dictionary Of Computing. 1996-01-28.
  3. Mac Plus, Billie's Apple Macintosh Museum. Accessed 2021-12-06.
  4. First of a New Breed by Jim Heid, Macworld p.94. 1995-08.

External links[]

  • SIMM at Computer Hope (2020-08-02)
  • SIMM at Wikipedia
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FOLDOC logo This page uses GFDL licensed content from the Free On-line Dictionary of Computing.