[SIMMS] [DIMMS] [SDRAM] [RamBuss] [DDRAM]

DIMM stands for Dual Inline Memory Module. The DIMM is different from the SIMM physically in that there are two   notches on the contact edge, and the module is slightly longer (5-1/4 inches instead of 4-1/4 inches). The DIMM module  inserts into its socket straight down, without the need for tilting. DIMM sockets have release  tabs at each end  which act as levers to push the module up out of the socket during removal.The most common DIMM is the 168-pin DIMM. The  connector for this type of DIMM has 168 positions. The edge connector is  double-sided so there are 84 positions on  each side of the connector edge.

DIMMs have become more specialized in recent months. The first type of DIMM was a page-mode design, typically  used  in the Power Mac.

A second type is the synchronous DRAM (SDRAM), which is measured in: Size (32, 64, or 128 MB),  Buffered/Unbuffered, Clocks (2 or 4), Voltage (3.3v), Speed(as megahertz or nanoseconds, 100 MHz=10ns). SDRAM comes in 2-clock and 4-clock  speeds. The clock speed can be thought of as a continual pulse that keeps  the system running in sync. Data is  pulled up in chunks with each pulse, and the 4-clock is a quicker pulse, so a module with the 4-clock spec has a faster response time than a 2-clock module.

The third type is the EDO DIMM. The EDO DIMM can be buffered or non-buffered, 3.3-volt or 5-volt, and may also be  ECC (Error Code Correcting). "x72" DIMMs are ECC. It is imperative to select the correct type of DIMM module  when upgrading. In order for us to send you the proper type of DIMM, we need to know the make  and model of your  computer. This will insure accuracy in your order.

The SODIMM is a "small-outline" DIMM, and is designed with a smaller form factor for use in notebook   computers. These are usually 72-pin modules. A smaller SODIMM (2-5/8 inches long) is also available which has 144 pins  and is used in newer notebook computers.