Socket 4 is a central processing unit (CPU) socket that semiconductor manufacturer Intel Corporation introduced in 1993 for its Intel Pentium computer chips. This device is responsible for connecting the CPU to the motherboard of a personal computer (PC) for data transmission purposes. It also provides physical support so that the processor does not suffer damage. Socket 4 was the first-ever Intel Pentium CPU socket, as well as one of the earliest CPU sockets that used the pin grid array (PGA) form factor.
PGA refers to the orderly grid-like layout of Socket 4’s 237 pin holes. They are for attaching the CPU via its pins. The pin contacts are arranged in four rows, which join each other on Socket 4’s square-shaped substrate. It uses a PGA variant called plastic pin grid array (PPGA), which denotes the plastic material used to make the socket. It has a zero insertion force (ZIF) feature to ensure that a user can remove or insert the CPU without using any force.
Socket 4’s predecessors, which were introduced between 1989 and 1991, were the Socket 1, Socket 2 and Socket 3, which contain 169, 238 and 237 pin holes, respectively. They were all made for the Intel 80486 microprocessor. Also known as the i486 and Intel486, the 80486 was named after its fourth-generational status in the lifespan of the 16-bit 8086, or iAPX86, chip that first appeared in the late-1970s.
That all changed, however, with Socket 4’s debut, as it was designed for Intel’s brand-new Pentium chip, which debuted on 22 March 1993. As the fifth generation of production of the 8086 brand, the Pentium’s microarchitecture was code-named P5, and it represented a major enhanced extension of this particular CPU family. In addition to the increase of pin holes, Intel bumped up the accommodated data transfer speed range from 16 to 50 megahertz (MHz) to 50 to 66 MHz. Coincidentally, the 50-to-66-MHz range was the entire processing-speed spectrum of the original generation of Pentium chips. Also, Socket 4 operates on a 5-volt (V) range.
Socket 4, however, is not the only socket that supports the original Pentium, which Intel began to phase out with the debut of the Pentium II in 1997 and ended production on two years later. By 1994, two more Pentium sockets had appeared, Socket 5 and Socket 7. These CPU sockets surpass Socket 4 with 320 and 321 pin holes, respectively. Also, they require considerably less operational voltage.