Dual In-line Memory Module (DIMM)

Last Updated: December 12, 2017

Definition - What does Dual In-line Memory Module (DIMM) mean?

A dual inline memory module (DIMM) is a small-scale circuit board that holds memory chips on the motherboard. DIMM incorporates a series of memory called dynamic random access memory (DRAM), which provides primary storage, the main memory that continually reads and executes stored instructions or data directly to the CPU.

DIMM is an attempt to improve on the earlier single inline memory module (SIMM), which used matched pairs. DIMM uses only one circuit board, thus increasing memory speed and storage. DIMM also has a much smaller circuit board and easier insertion compared to SIMM.

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Techopedia explains Dual In-line Memory Module (DIMM)

DIMM contains a series of DRAM integrated circuits. The modules are attached to a printed circuit board, with several RAM chips on a single circuit board, which is connected to the motherboard. With direct memory access (DMA), a PC processor can access any part of the memory directly without having to proceed in chronological order from a starting place. With DRAM, RAM accesses all parts of the memory directly.

RAM chips can be installed individually on a motherboard or in sets of chips on a miniature circuit board that plugs into the motherboard. The three most common circuit boards are:

Single Inline Memory Module (SIMM): A single in-line memory module with a 32-bit data path
Rambus Inline Memory Module (RIMM): Similar to SIMM but with a higher memory speed (RDRAM). Both SIMM and RIMM modules are installed in matched pairs.
Dual Inline Memory Module (DIMM): Has a separate electrical connector on both sides of the module. It stores each bit of data in a separate capacitor, providing direct access to the motherboard through the system bus.

Some memory modules have two or more independent sets of DRAM chips. These modules are connected to the same address and data bus. Each set of modules is called a rank. Only one rank can be accessed at a time because all ranks share the same bus. DIMM circuits are now being made with up to four ranks per module.