A single in-line memory module is a legacy printed circuit board carrying RAM chips that plugs into a motherboard socket. Unlike dual in-line memory modules, the contacts on both sides of a SIMM are redundant and carry the exact same electrical signals. They were widely used in older personal computers and embedded systems before being replaced by newer architectures that required distinct contacts on each side of the board to increase data bus width.
We had to hunt down a 72-pin SIMM to get that old industrial controller booting again.
Because the pins on both sides of the edge connector are tied together, they only provide a 32-bit data path, which is why older systems often required installing them in identical pairs.
Also heard as
- single in-line memory module
Do not mix it up with
- DIMM: A DIMM has independent electrical contacts on each side of the board to support wider data paths, whereas a SIMM ties the contacts on both sides together.
Related terms
DIMM
Dual in-line memory module, a printed circuit board holding memory chips used as main system RAM.
SODIMM
A compact memory module designed for laptops and space-constrained systems.
Motherboard
The main printed circuit board in a computer or complex electronic system routes power and data between major components.
Memory chip
An integrated circuit dedicated solely to storing digital data.