Desktop PC Memory (DIMM)

There is many RAM types available for desktop computers.  Most commonly used types are DIMMS (Dual In-Line Memory Module). DIMMS are small circuit boards that hold the memory chips, they are also standard in desktop computers.  Some of the more common types of DIMMS are:

1.     SDRAM – Synchronous Dynamic Random-Access Memory

·         Short for Synchronous DRAM, this type of DRAM synchronizes itself with the CPU’s bus.  Until recently, SDRAM was the memory standard.  When looking at SDRAM - The number following “PC” is telling you the speed of the system’s front side bus.  (example: The PC100 SDRAM is designed for systems equipped with a 100 MHz front side bus.)

2.     DDR-SDRAM – Double Data Rate Synchronous Dynamic Random-Access Memory

·         This is a type of SDRAM that supports data transfers on both edges of each clock cycle (note: the rising and falling edges), which effectively doubles the memory chip’s data throughput.  DDR-SDRAM is well-suited for notebook computers because it uses less power.  Some newer technologies that are replacing SDRAM are RDRAM, DDR-SDRAM, which is also called SDRAM ll and DDRAM.

3.     DDR2 SDRAM – Double Data Rate 2 Synchronous Dynamic Random-Access Memory

·         DDR2-SDRAM offers new features and functions that help enable a higher clock and data rate operations, DDR2 SDRAM is a step up from DDR-SDRAM.  DDR2-SDRAM memory is incompatible with the current DDR-SDRAM memory slots.  It also can transfer 64 bits of data twice every clock cycle.

4.     DDR2 SDRAM – Double Data Rate 2 Synchronous Dynamic Random-Access Memory

·         This is the third generation of DDR-SDRAM, as you can imagine there have been many improvements, including reduced power consumption, a double pre-fetch buffer, and it also offers more bandwidth because of its increased clock rate.

Laptop/Notebook Memory is Different (SO DIMM)

You will notice that most notebook/laptop manufacturers are commonly using the SO DIMM (Small Outline DIMM) memory modules, which are just smaller versions of the DIMM modules that are being used in desktop PC’s.  The differences in notebook RAM to desktop RAM is noticeable by it’s size difference and its pin configuration.  For instance, a full sized DIMM has 100, 168, 184, 240 pins and is most commonly 4.5 to 5 inches in length.  In contrast, a SO DIMM has 72, 100, 144, 200 pins and is considerably smaller – 2.5 to 3 inches.