Now we are using processors with GHz speeds but we must know the history of the very first processors. This article is about them.

The microprocessor is a semiconductor device consisting of electronic logic circuits manufactured by using either a large –scale (LSI) or very large-scale (VLSI) technique. The microprocessor is capable of performing computing functions and making decisions to change the sequence of program execution. In large computers, the CPU performs these computing functions and it is implementation on one or more circuit bonds. The microprocessor is in many ways similar to the CPU; however the microprocessor includes all the logic circuitry (including the control unit) on the chip.
8088
It is a grand old individual of PC CPU’s with 40-pin DIP package. It run 5MHz, 6.66, 7.16 or 8 MHz. Architecture is equivalent to 29,000 transistors. It supports 8-bit external data bus, (16-bit internal register) and 20-bit address bus. Depending on the address bus it can access 1 MB of RAM (640 KB of conventional memory and 384 KB of system BIOS). Normally 8088 CPU works at 4.77 MHz and in turbo mode it works at 8 MHz.
80186/80188
This is the next advanced generation of 8086/88 which system components, build in DMA and Interrupt controller. This is available Pin Grid Array (PGA) package and incompatible for IBM PC design. It was used for highly intelligent network peripheral cards. Also the CPU could not offer much performance improvement over earlier 8088.
80286
80286 introduced in 1982 used in IBM AT machine. It is five times faster than 4.77 MHz 8088 and handles 16-bit external data in Pin Grid Array package. The 286 chips are available in multiplex clock speeds. The available clock speeds are 6, 8, 10, 12.5, 16, and 20 MHz. It is also comes in PLCC (Plastic Leadless Chip Carrier) package. PGA has inner and outer square of solid pins and it stands on legs. While PLCC package has tinfoil like legs around perimeter. It uses 134,000 transistors. The 286 chips operate in two modes: Real mode and protected mode. In real mode, a 286 performs exactly like an 8088 having full object code compatibility with the 8086 and 8088. In protected mode of operation, the chip assumes that it has access to 1 GB of memory. This is due to a program designed to take advantage of the chips capabilities.
Introduced in 1985, the 286 chip is available in a 132 pin PGA package is equivalent to about 250,000 transistors and draws approximately 400 mille amperes of current, much less than the 8086. It is fabricated with CMOS technology, resulting in very low power consumption.
80386
The 386 are an advanced 32-bit processor designed for high-speed operation a multi tasking operating system. It has 32-bit internal registers and 32-bit internal/external data bus, which support 32-bit address and data types. The Intel 386 chip has various versions, with clock speeds ranging from 16 MHz to 33 MHz. OEMs offers comparable version with speeds up to 40MHz.
80386 SX/DX
It was introduced in 1985 as PGA package with 2,500,000 transistors that incorporates multi tasking features for OS/2 and windows. It has 32-bit data bus internally supports MCA, EISA, VESA and PCI bus. It addresses 16-bit data bus externally but handles 32-bit internally. It has a 24-bit address bus for addressing up to 16MB of physical memory. Its clocks speeds are 16MHz to 33MHz.
80386DX
It is a 32-bit CPU with 32-bit internal register and 32-bit internal data bus having 32-bit external data. It is available in 132 pins and consumes power of 400 mille amps. The architecture contains 275,000 transistors in VLSI (Very Large Scale Integration) circuit. Its clocks speeds 16MHz to 33MHz while OEM offers at 40MHz. It can up to 4GB of physical memory and 64TB of virtual memory.
80386 SL
It is 386SX with power management feature. Its extended architecture includes SMI (System Management Interrupt), SMM (System Management Mode) features and cache controller. It shutdowns the CPU between keystrokes, saving power, used in laptop system. It is available in PLCC package at 25MHz speed SL based processor are used in notebook computers.
486PROCESSOR
In April of 1989, Intel announced the 486 processor. The 80486 microprocessor is a 32-bit architecture which an on chip memory management unit (a tuned – up 386), FPU (387 numeric coprocessor) and a cache memory unit (385 cache controller). Over 1.2 million transistors are integrated in to this chip. This enables a 25MHz 486 to execute twice the number of instruction as compared to a 25MHz 386 with a 385 and 387. Since its introduction, many versions of the 486 chips have been made available. A part forms certain common features like full 32-bit architecture and a built in a 8K memory cache. The various family members of the 486 have certain unique features like their maximum speeds and pick configuration. Some of the 486 family members are listed blow:
CPU Type Specifications Available Speed (In MHz)
486SX similar to 80486 without 16, 20, 25, 33
Numeric coprocessor
486DX Same as 80486 25, 33, 50
486DX2 80486 at double speed 40, 50, 66
486DX4 80486 at triple speed 75, 100
The microprocessor can always operate at speeds lower than its rated speed. For example, you can plug in a 50MHz 486DX into a 33MHz system.
486DX PROCESSOR
The first chips had a maximum speed rating of 25MHz, later version of the 486DX where available in 33MHz and 50MHz rated version. The 486DX originally was available only in 5V, 168 – pins PGA (Pin Grid Array) version, but now is also available 5V, 196 – pins PQFP (Plastic Quad Flat pack) and 3.3v, 208 – pin SQFP (Small Quad Flat Pack) as well. The 486DX integrate function such has the math coprocessor, cache controller and cache memory in to the chip. It has 1.25 millions transistors. The 486DX processor is fabricated with low- power CMOS technology. The chip has a 32 – bit internal register size, a 32-bit externally data bus, and 32-bit address bus. This dimensions are equal those of the 386DX processor.
486SX PROCESSOR
The 486SX virtually identical to the full DX processor, but the chip does not incorporate the FPU or math coprocessor portion. The 486Sx chip is twice as fast as a 386DX with the same clock speed. The 486SX was normally available in 16, 20, 25, and 33MHz rated speeds, and there are also a 486SX /2 that ran at up to 50 or 66MHz. It is available in 168-pin version.

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