Single in-line memory module

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.

Description
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 s (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. These have since been superseded by dual in-line memory modules (DIMMs).

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