DIMM (Dual In-line Memory Module) is an assembly of several memory chips on a single PCB used to upgrade RAM capacity. DIMMs have gradually replaced SIMMs used in earlier machines. SIMMs only had contacts on one side of the card. DIMMs have contacts on both sides that hold twice as many chips as a SIMM. DRAM and SDRAM are two types of memory chips used in DIMMs. Extended Data Out (EDO) DRAM is the most common type of asynchronous DRAM used. At times it is also called hyper page mode DRAM.
DIMMs gradually began replacing SIMMs as the predominant type of memory module when Intel's Pentium processors were in the mainstream market.
The most common types of DIMMs are:
72-pin-DIMMs, used for SO DIMM
144-pin-DIMMs, used for SO DIMM
168-pin-DIMMs, used for SDRAM
184-pin-DIMMs, used for DDR SDRAM
240-pin-DIMMs, used for DDR2 SDRAM
