Intel Processors, the History

Intel was one of the pioneering Microprocessor manufacturers when it created the 4004 processor in 1971. This was followed by the 8080 processor in the late 70's, which was developed into the 8086 and 8088 processors in 1979. It was only when, in 1981 IBM selected the 8086 processor for its new Personal Computer, the IBM PC, did the Intel processor design gain its opportunity to be used widely.
The Intel 8086/8088 range of processors were based upon Complex Instruction Set Computing (CISC) which allows the number of bytes per instruction to vary according to the instruction being processed. This is unlike Reduced Instruction Set Computing (RISC) which has fixed length instructions (typically set at 32 bits each). The architechture pioneered by Intel has become known as "x86" due to the early naming system where processors were called 8086, 80186 (not used in PC's), 80286, 80386, and 80486.
In 1982 Intel introduced the 80286 (or 286) processor. This featured significant enhancements over the 8086/8088 line, mainly by introducing protected mode and the ability to address up to 16 megabytes of memory. The 286 processor was used in the IBM XT range.
1985 saw the introduction of the 80386 (or 386), which was the first processor to use 32 bit addressing, allowing it to utilise up to 4 Gigabytes of memory. A cut down version of the 386 known as the 386SX was introduced which had a lower memory throughput, as it could only access 16 megabytes of memory. The 386 processor was manufactured in many different versions and ran at speeds from 16 Mhz through to 40 Mhz.
The 80486 processor family was introduced in 1989. It featured little enhancements over than the 386 other than the fact that it had more transistors and could run at higher clock speeds. Like its predecessor the 386, the 486 was offered in budget (486 SX, minus the math co-processor) and standard (486 DX) versions. The 486 initially ran at clock speeds of 25 MHz (SX only) and 33 MHz. As it was developed the 486 was enhanced with a clock doubled processor core (486 DX-2) allowing it to run at speeds of 50, 66 and 75 MHz, and then tripled (DX-4) which ran up to 100 MHz.
1993 saw the introduction of the Pentium processor, first at speeds of 60 and 66 MHz. This was the first Intel processor not to use the x86 naming system. This processor was enhanced with MMX instructions in January 1997 and ran up to speeds of 233 Mhz.
Intel's 6th generation processor was introduced as the Pentium Pro in 1995. This ran at speeds of 166, 180 and 200 MHz. What was significant was the integration of the processors 2nd level cache memory onto the processor module itself. This processor was enhanced with MMX instructions in 1997 with its development into the Pentium II. This marked a departure for Intel as it moved away from the old socket method of mounting processors with the introduction of Slot 1. The Pentium II runs at speeds from 233 to 450 MHz. 1998 saw the development of this familiy into the Celeron and Xeon families for the budget and server/workstation markets respectively.