(SIMM) A small circuit board or substrate, typically about 10cm x 2cm, with RAM integrated circuits or die on one or both sides and a single row of pins along one long edge. Several SIMMs are mounted with their substrates at right-angles to the main circuit board (the motherboard). This configuration allows greater packing density than direct mounting of, e.g. DIL (dual in-line) RAM packages on the motherboard. In 1993 one SIMM typically held one or four megabytes, by early 1997 one could hold 8, 16, or 32 MB.