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A PGA socket refers to a type of central processing unit (CPU) socket that uses the pin grid array form of integrated circuit packing. With PGA, pin holes of the socket are neatly arranged in a grid, which is an equally spaced-out network of horizontal and vertical lines crossing each other. This framework is used to give the PGA socket a structured format. The pins or pin contacts of a PGA socket are usually spaced no more than 0.1 inches (2.54 millimeters) apart on a square-shaped structure.
A motherboard, which serves as the “heart” of the personal computer (PC), is where the PGA socket is mounted. Also called a main board or printed circuit board, the motherboard contains many of the major components and functions of a PC, such as audio jacks, video display connectors, graphics card, connectors for the hard disk and optical drives, and system memory. The CPU socket is for connecting the CPU, or processor, of the PC to the motherboard for conducting data transmission.
The PGA socket also protects the computer chip from possible damage when one plugs it in or removes it. Most PGA sockets use zero insertion force (ZIF), which requires no force at all for insertion and removal, and sometimes may involve a lever to aid in such actions. A much less popular standard is low insertion force (LIF), which requires very little force and also may include a lever.
There are a significant number of PGA variants. The three most popular ones are the plastic pin grid array (PPGA), flip-chip pin grid array (FCPGA) and organic pin grid array (OPGA). PPGA means that the socket is made of plastic, and the OPGA distinguishes itself in that it is made of organic plastic. FCPGA denotes the CPU being flipped to expose its back, making it ideal for a heatsink to be introduced and dissipate the heat that it produces.
In the early 1980s, integrated circuit manufacturers began making PGA sockets. Within the next two decades, the grid-based layout was dominating the integrated circuit market. One of the major reasons for this popularity was because it could accommodate more pins than could previous packages. For instance, the single in-line package (SIP) usually contains a row of nine pins, and the dual in-line package (DIP) offers two rows, totaling 14 pins.
By contrast, PGA sockets can offer a pin count almost reaching 1,000. An example is the Socket 939, which was released by semiconductor manufacturer Advanced Micro Devices and has the most pin contacts of any PGA socket as of May 2011. In 2008, however, manufacturers started using the land grid array (LGA) form factor, and it eventually overtook the PGA.