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DIMM (dual in-line memory module)

By Linda Rosencrance

What is DIMM (dual in-line memory module)?

DIMM, or dual in-line memory module, is a type of computer memory that is natively 64 bits, enabling fast data transfer.

DIMM is a module that contains one or several random access memory (RAM) chips on a small circuit board with pins that connect it to the computer motherboard. The DIMM stores each data bit in a separate memory cell.

How DIMMs work

DIMMs use a 64-bit data path, since processors used in personal computers have a 64-bit data width. DIMMs are typically used in desktop PCs, laptops, printers and other devices.

A SIMM, or single in-line memory module, typically has a 32-data-bit path to the computer that requires a 72-pin connector. For synchronous dynamic RAM (SDRAM) chips, which have a 64-data-bit connection to the computer, SIMMs must be installed in in-line pairs, since each one supports a 32-bit path. A single DIMM can be used instead. Originally, DIMMs had a 168-pin connector to support 64-bit data transfer.

As faster dynamic RAM (DRAM) was developed, DIMM circuit boards evolved. Modern DIMMs based on fourth-generation double data rate (DDR4) SDRAM chips use 288-pin connectors to attach to the computer motherboard to enable the increase in data throughput. As clock speeds of the RAM chips increased, the 64-bit path handled increasing amounts of data.

Another evolution in DIMMs is the use of cooling fins or structures attached directly to the DIMM. The increase in chip density in typical 8 gigabyte or 16 GB DIMMS, and the increase in clock speed, led to an increase in heat production. This was made worse by the fact that DIMMs based on DDR4 RAM chips can be produced in capacities up to 64 GB.

Cooling structures on the DIMM help vent that heat into the computer enclosure and away from the motherboard and central processing unit (CPU).

Types of DIMM

The most common standard DIMMs, with a typical length of 5.5 inches and height of 1.18 inches, include the following:

Editor's note: This article was revised in 2024 by TechTarget editors to improve the reader experience.

22 Mar 2024

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