A memory module which is added to a computer to increase its amount of random access memory. A single SIMM contains several memory chips, usually rows of eight or nine individual chips, each with a capacity of 256 kilobits, 1 megabit, or 4 megabits. SIMMs are mounted to the computer's motherboard, and are usually used on Macintosh computers. Newer Macs utilize double in-line memory modules, also known as DIMMs. A SIMM is much like a single in-line package, save that the SIMM plugs into the motherboard by means of a contact slot.