What is a CPU Socket?

A computer’s central processing unit (CPU) is the chip that performs most of the calculations for the computer’s operating system and applications. The CPU has a special mount on the motherboard called the CPU socket. This mount will only fit a CPU; no other computer chip will fit on it. In addition to holding the processor, it has a lock for keeping the processor in place and a special design so it can secure the heat sink that will go on top of the processor.

A CPU socket may be found on most standard desktop and many server systems. Laptops and some types of server systems may use a different style of processor. The socket itself is generally a square of single-colored plastic with a hole in the middle, like a doughnut, and a lever on one side. This plastic is often a cream or burgundy color, but color is a choice of the manufacturer rather than a specification. The plastic has hundreds of pin holes in rows that completely cover the surface.

Each CPU socket is designed for a specific group of CPUs. A socket may take a specific CPU classification or group from a single manufacturer. The exact details of which sockets take which CPUs vary based on the age and manufacturer of the socket and motherboard. Most sockets have a three to five digit number printed on one side of the socket. This number allows users to look up the exact model and determine what types of processors the CPU is supposed to hold.

A CPU socket is used in a very specific way. The user fist needs to raise the lever on the side of the socket; the processor chip is then placed on the socket so the pins on the chip drop into the pin holes on the socket. Most chips will only fit in a socket one way, while others have a line-up feature. This insures that users won’t insert the CPU incorrectly. The lever is then pushed back down into its original position. This lever action will lock the chip in place, both preventing it from moving and assuring a good electrical connection.

After the processor is in, the CPU socket still has room to hold the heat sink. Since processors make so much heat, they have a specialized heat sink and fan system that sits on top of them. Heat sinks have a bracket on two sides. The heat sink is placed on top of the processor and both sides of the bracket are hooked onto the CPU socket. The clamp on the side of the bracket is pushed down, often with a specialized tool or flathead screwdriver, until the heat sink locks in place. At this point, most CPU sockets are completely covered by the components.