Pictures of Selected RAM Form Factors
SIMM (Single-Inline Memory Module). Used mainly in older computers; now considered obsolete. Its contacts were along only one face of the edge, hence the word "single."
DIMM (Dual-Inline Memory Module). The most common RAM form factor in use today.
SDRAM and DDR-SDRAM are examples of two types of RAM using the DIMM form factor.
SO-DIMM (Small-Outline Dual-Inline Memory Module). Used primarily in laptop computers and other compact computing devices.
RIMM (Rambus Inline Memory Module). Rambus is high-end RAM for motherboards using Intel's i820/i840 chipsets.
RDRAM is very fast -- and very expensive.