SIMM or single in-line computer memory module. The first SIMM modules had 30 pins and transferred data 8 bits at a time. As 32-bit computing developed, wider 72-pin SIMMs were developed that could transfer data at 32 bits.

DIMM or dual in-line computer memory module. DIMMs look similar to SIMMs, except that the DIMMs are longer 168 pins to be exact, and the pins on the opposing sides of the computer memory module are electrically isolated from...

SIMM or single in-line computer memory module. The first SIMM modules had 30 pins and transferred data 8 bits at a time. As 32-bit computing developed, wider 72-pin SIMMs were developed that could transfer data at 32 bits.

DIMM or dual in-line computer memory module. DIMMs look similar to SIMMs, except that the DIMMs are longer 168 pins to be exact, and the pins on the opposing sides of the computer memory module are electrically isolated from each other.

RIMM These modules look similar to DIMMs but generate more heat because they provide faster access and transfer speeds. RIMMs come with an aluminum heat spreader that covers the module. DIMMs have the same number of pins (184) as a DDR DIMM, but a RIMM can only be used on motherboards or systems specifically designed for RIMMs.

SO DIMM (small outline) and MicroDIMM. Laptops or notebooks use SO DIMMs. Smaller sub-notebook devices typically use MicroDIMMs.

These cards can be identified on a system Motherboard MOBO as the long slender modules usually with free banks beside them