A SIPP or single in-line pin package was a type of random access memory.

It consisted of a small printed circuit board

Printed circuit board

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...

 upon which were mounted a number of memory chips. It had 30 pins along one edge which mated with matching holes in the motherboard

Motherboard

In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...

 of the computer.

This type of memory was used in 80286 and some 80386 systems. It was later replaced by SIMM

SIMM

A SIMM, or single in-line memory module, is a type of memory module containing random access memory used in computers from the early 1980s to the late 1990s. It differs from a dual in-line memory module , the most predominant form of memory module today, in that the contacts on a SIMM are redundant...

s, which proved to be easier to install.

30-pin SIPP modules were pin compatible with 30-pin SIMM modules explaining why some SIPP modules were in fact SIMM modules with pins soldered onto the connectors.