What kind of memory is this?

Most of the memory we are run into at Free Geek, falls into one of two categories (DIMM and SIMM):

DIMM

Dual Inline Memory Modules are newer and longer than the older SIMMs (see below). All DIMMs are the 5.25 inches long, and they can be distinguished by the number and positions of their notches.

SDRAM

A stick of SDRAM has two notches in it, one near the center of the stick, and one closer to the side.

DDR

A stick of DDR has a single notch in it near the center of the stick.

RAMBUS

A stick of RAMBUS has two notches in it at the center of the stick.

SIMM

Single Inline Memory Modules are older and shorter than the DIMMs. There are two varities, 30-PIN SIMMs and 72-PIN SIMMs. Both are substantially shorter than the DIMMs (above). We normally do not want to keep SIMMs these days.

72 Pin SIMM

72 pin SIMMS are 4.25 inches long. This is about the same length as a cache module, but the holes and notches to install them are different, see points A (side holes), B (center notch) and C (side notch) in the picture.

NOTE: The 72-PIN SIMM is not a DDR (because it's not a DIMM and all DDRs are DIMMs). Many people confuse these types of memory, because both have only one notch. The 72-PIN SIMM is much too short to be a DDR.

30 Pin SIMM

30 pin SIMMs are 3.5 inches long. These are the oldest types of memory we tend to see very often. Note that they do not have a center notch.