Evolution of Intel Processors Part 1

8086 Processor Evolution

Intel 8086

This was introduced in June 8, 1978. It was available in different clock speeds: 5 MHz with 0.33 MIPS; 8 MHz with 0.66 MIPS and 10 MHz with 0.75 MIPS. The memory is divided into odd and even banks. It accesses both the banks simultaneously in order to read 16 bit of data in one clock cycle. The width of the bus is 16 bits, and uses 20 bit addresses. The processor consists of 29,000 transistors. The performance of 8086 is 10 times the performance of 8080 processor.

Intel 80286

This was introduced February 1, 1982 as advancement to Intel 8086 processor. Was available in different clock speeds than 8086: 6 MHz with 0.9 MIPS; 8 MHz, 10 MHz with 1.5 MIPS; 12.5 MHz with 2.66 MIPS. Also available in 16 MHz, 20 MHz and 25 MHz. Bus width remains unchanged as 16 bits. Includes memory protection hardware to support multitasking operating systems with per-process address space. Processor consists of 134,000 transistors at 1.5 μm. It also has 16MB of addressable memory. Instruction set is as same as 8086, but has additional features of protected-mode. The processor exhibits 3 to 6 times better performance than 8086. These processors are widely used in IBM-PCs.

Intel 80386

Intel 80386 as introduced on October 17, 1985. This processor is commercially known as 386 DX. Uses a clock with frequency of 16.0 MHz, and handles 5 million instructions per second (5 MIPS). The processor composed of 275,000 transistors. How ever it maintains the same width of address bus, 16 bits.

Intel 80486

This was introduced as advancement to Intel 80386 on April 10, 1989, and commercially known as 486 DX. Frequency of clock is 25.0 MHz. Compared to Intel 80386, the number of instructions handled per second has become 4 times (20 MIPS). Also, the number of transistors used has been increased to 1.2 million, and it is more than 4 times of the number of transistors used in Intel 80386. For the first time in 8086 family,the width of the address bus has been increased from 16 buts to 32 bits.

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