CPU Socket Identification by Processor Type:


486 Socket Identification
---------------------------
   
   Most 486 systems use PGA (Pin Grid Array) style sockets, but some
   486 processors are soldered directly to the motherboard.  Standard
   486 CPUs use 168 pin PGA sockets with the pins arranged in a 17 
   by 17 grid. However, some systems use larger OverDrive sockets. 
   OverDrive socket #1 has 169 pins in a 17 by 17 grid, OverDrive 
   socket #2 has 238 pins in a 19 by 19 grid, and OverDrive socket #3
   has 237 pins in a 19 by 19 grid. There are two types of 486 PGA 
   sockets: LIF (Low Insertion Force) sockets are standard PGA sockets
   which require a removal tool for processor removal; ZIF (Zero 
   Insertion Force) sockets have a lever built into the socket which
   is used to release the processor from the socket for easy removal 
   without a special tool.


386DX Socket Identification
---------------------------
 
   The 386DX microprocessor is an 1 1/2" square, ceramic chip, and 
   socketed on the motherboard (or, rarely, on a card). Most 386DX 
   microprocessors are socketed on the motherboard using Pin Grid Array
   (PGA) socket. However, a few models are soldered into their sockets. 
   386DX CPUs that are soldered are not compatible with REV TO 486 
   upgrade.


386SX Socket Identification
---------------------------

   The 386SX microprocessor is a square, black chip, made of plastic, 
   that is soldered on the motherboard (or, rarely, on a card). It is
   3/4 inch sqaure with tabs at each corner.


286 Socket Identification
-------------------------

   There are three socket styles for the 80286 CPUs: PGA, PLCC, and LCC.


   PGA (Pin Grid Array) Identification
   -----------------------------------

   The Pin Grid Array (PGA) 286 microprocessor is found in IBM models
   IBM AT, IBM XT286, and IBM PS/2 models 50 and 60. The PGA socket style
   is also used in NEC Powermate and a few other clones. PGA 286 chips 
   are approximately 1" square, and made of purplish-gray ceramic 
   material. They have gold pins extending from the bottom of the chip 
   and are housed in a 68-pin socket. No pins are visible until the PGA
   chip is removed from its socket.


   PLCC (Plastic Leaded Chip Carrier) Identification
   -------------------------------------------------

   The Plastic Leaded Chip Carrier (PLCC) is the most common CPU used by 
   manufacturers such as AST, Compaq, Epson, Acre, Sperry, and HP. These 
   manufacturers also use the LCC chip socket (see next section for LCC 
   identification). PLCC chips are 1" square and 1/4" thick and are made
   of black plastic with J-pins on all four sides. PLCC chips sit in a 
   square socket, and have a dot and a beveled corner indicating Pin 1.

   Note: Some PLCC chips are soldered directly to the motherboard. PLCC
   chips soldered to the motherboard are incompatible with the 
   REV TO 486 upgrade.


   LCC (Leadless Chip Carrier) Identification
   ------------------------------------------

   The Leadless Chip Carrier (LCC) has a heat sink or metal shroud over
   the top of the chip, which helps dissipate heat. The LCC socket is 
   used by many clone manufacturers (Packard Bell, Tandy, Convergent
   Technologies, etc). The LCC has no pins either on the sides or the 
   bottom. Electrical contact is made on the gold surface on the bottom
   of the chip, which is held by a clamp.



File Name    : SOCKETS.TXT
Last Updated : 05/23/96