The Intel x86 Architecture

The Intel x86 Architecture

Introduction
In 1978 Intel had a 16-bit successor to the 8080, the 8086/8088. The 8088 was internally identical to the 8086 with the exception of an 8-bit external data bus, rather than 16-bit. Certainly this would limit the performance of the device. The growth of the PC industry essentially tracked Intel’s continued development and ongoing refinement of the x86 architecture.
Intel introduced microprocessors way back in 1969. Their first 4-bit microprocessor was the 4004. This was followed by the 8080 and 8085. The work on these early microprocessors led to the development of the Intel architecture (IA). The first processor in the IA family was the 8086 processor. It has a 20-bit address bus and a 16-bit data bus. Thus, it could address up to 1 MB of memory.
The 8088 is a less expensive version of the 8086 processor. The cost reduction is obtained by using an 8-bit data bus. Except for this difference, the 8088 is identical to the 8086 processor. Intel introduced segmentation with these processors. These processors can address up to four segments of 64 KB each. This IA segmentation is referred to as the real mode segmentation.
The 80186 is a faster version of the 8086. It also has a 20-bit address bus and 16-bit data bus, but has an improved instruction set. The 80186 was never widely used in computer systems. The real successor to the 8086 is the 80286, which was introduced in 1982. It has a 24-bit address bus, which implies 16 MB of memory address space. The data bus is still 16 bits wide, but the 80286 has some memory protection capabilities.