DIMMs have a 168-pin connector and, since the advent of the Pentium Processor, a 64-bit path. Because of the new bit path, DIMMs can be installed one at a time, unlike SIMMs that would require installation in pairs.
SO-DIMM, which is short for Small Outline DIMM, is available in both a 72-pin and 144-pin configuration. SO-DIMMs are commonly utilized in laptop computers. Below is an example picture of a 4GB SODIMM memory stick from Crucial.
Advantages DIMMs have over SIMMs
DIMMs have separate contacts on each side of the board, which provides twice as much data as a single SIMM.
The command address and control signals are buffered on the DIMMs. With heavy memory requirements, this buffering reduces the loading effort of the memory.