UniDIMM

UniDIMM (short for Universal DIMM) is a specification for dual in-line memory modules (DIMMs), which are printed circuit boards (PCBs) designed to carry dynamic random-access memory (DRAM) chips.

[6][1]: 28  UniDIMMs have a 260-pin edge connector, which has the same pin count as the one on DDR4 SO-DIMMs,[5] with the keying notch in a position that prevents incompatible installation by making UniDIMMs physically incompatible with standard DDR3 and DDR4 SO-DIMM sockets.

In previous RAM standard transitions, as it was the case when DDR2 was phased out in favor of DDR3, having an emerging RAM standard as a new product line created a "chicken-and-egg" problem because its manufacturing is initially more expensive, yields low demand, and results in low production rates.

The DDR2 to DDR3 transition issues were sometimes handled with specific motherboards that provided separate slots for DDR2 and DDR3 modules, out of which only one kind could be used.

[6] As of April 2018[update], UniDIMM is not standardized by JEDEC,[2] having Kingston and Micron as its main supporters.