The Free On-line Dictionary of Computing (30 December 2018):

x86 processor socket
Socket 1
Socket 2
Socket 3
Socket 4
Socket 5
Socket 6

    One of the series of standard sockets
   into which you can plug various x86 microprocessors.
   These vary in the number of pins, package, voltages, bus
   speeds, and supported processors.  Motherboards often have
   clock multipliers so that the processor runs at a multiple
   of the bus speed.

   Socket 1, 169 pin LIF/ZIF PGA (17x17), 5v, 16-33 MHz
   486 SX, 486 DX, 486 DX2, DX4 Overdrive.  Socket 1 was
   the first standard Intel 486 socket.

   Socket 2, 238 pin LIF/ZIF PGA (19x19), 5v, 25-50 MHz 486 SX,
   486 DX, 486 DX2, 486 DX4, DX4 & Pentium Overdrive.  Updated
   Socket 1, added support for Pentium Overdrive processors.

   Socket 3, 237 pin LIF/ZIF PGA (19x19), 3.3/5v, 25-50 MHz 486
   SX, 486 DX, 486 DX2, 486 DX4, DX4 & Pentium Overdrive.
   Supports 5V & 3.3V processors, considered the latest 486
   socket.

   Socket 4, 273 pin LIF/ZIF PGA (21x21), 5v, 60/66 MHz Pentium
   60/66 and Pentium Overdrive, only 5v.

   Socket 5, 296 pin LIF/ZIF, 320 pin LIF/ZIF SPGA (19x19 or
   37x37), 3.3v, 50/60/66 MHz Pentium 75 - 133MHz, Pentium
   Overdrive, only 3.3v.

   Socket 6, 235 pin ZIF PGA (19x19), 3.3v, 25-40MHz.  Unpopular
   advanced Socket 3, rarely seen / paper spec 486 DX4, Pentium
   Overdrive, only 3.3v.

   See also Socket 7, Socket 8, Super 7, Slot 1, Slot
   2, Slot A.

   CPU Sockets chart
   (http://users.erols.com/chare/sockets.htm).

   CPU Sockets (http://webm3308.ntx.net/cpusockets.htm).

   (1999-08-05)