If you’ve ever upgraded your computer’s memory, you have probably heard of SODIMM, or Small Outline Dual In-line Memory Module. It’s a type of RAM that uses integrated circuits. SODIMMs are about half the size of the regular DIMMs, which makes them perfect for smaller devices like notebook computers, upgradeable printers, and networking devices like routers.

SODIMMs come in several different varieties that can be identified by the number of pins on the chip. There are 72, 100, 144, 200, and 204 pin varieties. SODIMMs with 72 or 100 pins only support 32-bit data transfer rates, while the higher pin SODIMMs can handle 64-bit transfer rates. These chips are comparable to DIMMs with 168, 184, and 240 pins.

It’s easy to visually identify SODIMM chips. They feature two very distinctive notches on the chip itself. These notches differ: 100-pin SODIMMs have two, while 144-pin SODIMMs have one notch close to the center of the chip. 200-pin SODIMMs have a notch off to one side, although this notch has two possible locations. If it is not near the center, it can be used to indicate the class of DDR memory. If the notch is near the center, for example, the piece of RAM is most likely DDR2.

It’s important to note that these types of RAM are not interchangeable, so it is very important for those upgrading their computers to purchase the correct type. Because the notches are in different places, it is not possible to accidentally install the wrong type of RAM in a computer. Likewise, because of the size difference, you cannot put a SODIMM chip in a DIMM slot.

When it comes to voltage and power, SODIMMs and DIMMs are about equal. They are available in the same speed options. RAM speeds of 1066 MHz and even faster are becoming quite common these days. Because the two types of RAM are evenly matched in speed and transfer rates, the only true difference is in their size. Because they’re smaller, SODIMMs are used in laptops, while DIMMs are generally used in desktop computers.