PC Hardware in a Nutshell, Second Edition

Intel Processors

Nearly all PCs use either an Intel CPU or an Intel-compatible CPU made by AMD (K6/Athlon/Duron series). The dominance of Intel in CPUs and Microsoft in operating systems gave rise to the hybrid term Wintel, which refers to systems that run Windows on an Intel or compatible CPU. Intel processors are referred to generically as x86 processors, based on Intel’s early processor naming convention, 8086, 80186, 80286, etc. Intel has produced seven CPU generations, the first five of which are now obsolete and the sixth obsolescent.

First generation

The 8086 was Intel’s first mainstream processor, and used 16 bits for both internal and external communications. The 8086 was first used in the late 1970s in dedicated word processors and minicomputers like the DisplayWriter and the System/23 DataMaster. When IBM shipped their first PC in 1981, they used the 8088, an 8086 variant that used 16 bits internally but only 8 bits externally, because 8-bit peripherals were at that time more readily available and less expensive than were 16-bit components. The 8086 achieved prominence much later when Compaq created the DeskPro as an improved clone of the IBM PC/XT. A few early PCs, notably Radio Shack models, were also built around the 80186 and 80188 CPUs, which were enhanced versions of the 8086 and 8088 respectively. The 8088 and 8086 CPUs did not include a floating-point unit (FPU), although an 8087 FPU, called a math coprocessor, was available as an optional upgrade chip. First-generation ...