PC CPU models

The brains of the PC is a central processing unit (CPU) made by Intel or AMD (Advanced Micro Devices). It stems from the Intel 8086 architecture (x86) used in the first PC in 1981. Following are the major classes of PCs based on their CPU, starting with the most current.

Pentium Class

Pentium, Celeron and Xeon from Intel
In 1993, the Pentium family was introduced by Intel, and numerous models have been developed. Pentium chips range in performance from entry-level desktop machines (Celeron and Pentium) to high-end servers (Xeon). In 2001, Intel introduced the Itanium, a next-generation chip that uses a different architecture than the x86 line, but runs x86 applications. See Pentium, Celeron, Xeon, Itanium and PC operating environments.

Athlon, Duron, Sempron and Opteron from AMD
Starting in 1994, AMD introduced its first Pentium-compatible CPU, the K5. It was followed by the K6 and then the Athlon line in 1999. The Duron was subsequently introduced for the value market to compete with Intel's Celeron, and Duron chips were superseded by the Sempron in 2004. In 2003, AMD debuted the Opteron, the first x86-compatible 64-bit CPU.

Earlier CPUs

386 and 486 from Intel
Am386, Am486 and Am5x86 from AMD
First used by Compaq in 1986, Intel's 386 introduced an enhanced architecture that has been carried forth in all subsequent chips, including the 486 and Pentium models. The 386 brought a 32-bit mode of operation and the ability to address 4GB of memory, although even today, most PC motherboards cannot hold anywhere near that amount. Even the 32-bit mode was rarely used until Windows 95 was introduced. In late 1989, the 486 came out, offering faster speed and a built-in math coprocessor, required by CAD programs.

In 1991, AMD introduced the Am386, the first 386-compatible CPU, which was followed by two 486-compatible models, the Am486 and Am5x86. See 386, 486 and AMD.

286 from Intel - AT Class
First used in the IBM AT in 1984, Intel's 286 was a 16-bit CPU that addressed 16MB of memory. ATs were just faster XTs, and memory above 1MB was rarely used for applications until Windows 3.0 became popular. By then, 386s and 486s were widely available. AT-class machines ran DOS and were extremely sluggish under Windows. See 286.

8088 from Intel - XT Class
The original PC launched by IBM in 1981 used Intel's 16-bit 8088 CPU. This chip family was designed so that the installed base of CP/M applications could be easily ported to the new architecture. See 8088 and CP/M.

The 8088 was limited to one megabyte of memory and had a simple architecture; nobody knew it would evolve into the world's largest hardware standard. Subsequent 32-bit 386, 486 and Pentium CPUs also included a 16-bit operating mode to conform to the original standard in order to run all the DOS and 16-bit Windows 3.x applications on the market. Such applications are still used today, running in CPUs with clock speeds a thousand times faster than the 8088. You may find an XT-class machine at a computer flea market.