Memory Modules

Memory Modules

Memory modules, properly known as memory board is device where DRAM integrated circuit are installed or mounted. These allow easy installation and replacement in system such as PC, workstation and more.


Dual Inline Memory Module (DIMM) is a memory module residing on computer’s motherboard. It is basically a long and thin circuit board with tabs along one edge; the tabs are engrossed with flat metal pins used for transferring data between the computer and RAM. RAM is a black module placed on the surface of DIMM.

A DIMM memory module has a 168-pin connector and a data transfer rate of 64 bits. This is faster as compared to SIMM. Figure 14 shows a 168-pin DIMM.DIMM provides assistance to the computer in processing memory. It connects to the computer data bus. It can also help in error detection and a few DIMMs are called Error Correction Code (ECC) enabled DIMMs. Computer motherboards for home use are not designed for these DIMMs.

The DDR used in desktop memory is packaged in 184-pin DIMMs and DDR2 and DDR3 are packaged in 240-pin DIMMs but are incompatible.



The standard RAM packages such as DIMM cannot be used for laptop or other computers requiring much smaller components. RAM of such computers is packaged in a smaller module known as Small Outline DIMM (SODIMM).

There are various physical implementations of SODIMMs such as the old 32-bit (72 and 100-pin) configuration and new 64-bit (144-pin SDR SDDRAM, 200-pin DDR/DDR2 and 204-pin DDR3) configuration.

All 64-bit modules have single keying notch; the notch in 144-pin module is slightly off-centre. For DDR and DDR2, 200-pin SODIMMs have different key position. These SODIMMs are non-interchangeable.

It may happen that data in memory may get corrupted while transferring to and from memory prevent Hence, it becomes essential to detect error caused to prevent hazardous situations. Motherboards use a simple error detection mechanism known as parity checking. The following subsection discusses about this method.


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