Microprocessor | Intel x86 evolution and main features

Intel x86 architecture has evolved over the years. From a 29, 000 transistors microprocessor 8086 that was the first introduced to a quad-core Intel core 2 which contains 820 million transistors, the organization and technology have changed dramatically. Some of the highlights of the evolution of x86 architecture are:

1. 8080 – It was the world’s first general-purpose microprocessor. It was an 8-bit machine, with an 8-bit data path to memory. It was used in the first personal computer.
2. 8086 – It was a 16-bit machine and was far more powerful than the previous one. It had a wider data path of 16-bits and larger registers along with an instruction cache or queue that prefetches a few instructions before they are executed. It is the first appearance of 8086 architecture. It has a real mode and an addressable memory of 1 MB.
3. 80286 – It has an addressable memory of 16 MB instead of just 1 MB and contains two modes-real mode and first-generation 16-bit protected mode. It has a data transfer width of 16-bits and a programming model of 16-bits (16-bits general purpose registers and 16-bit addressing).
4. 80386 – It was Intel’s first 32-bit machine. Due to its 32-bit architecture, it was able to compete against the complexity and power of microcomputers and mainframes introduced just a few years earlier. It was the first processor to support multitasking and contained the 32-bit protected mode. It also implemented the concept of paging (permitted 32-bit virtual memory address to be translated into 32-bit physical memory address). It has an addressable physical memory of 4 GB and a data transfer width of 32 bits.
5. 80486 – It introduced the concept of cache technology and instruction pipelining. It contained a write protect feature and offered a built-in math co-processor that offloaded complex math operations from the main CPU.
6. Pentium – The use of superscalar techniques was introduced as multiple instructions started executing in parallel. The page size extension (PSE) feature was added as a minor enhancement in paging.
7. Pentium Pro – It used register renaming, branch prediction, data flow analysis, speculative execution, and more pipeline stages. Advanced optimization techniques in microcode were also added along with level 2 cache. It implemented the second-generation address translation in which a 32-bit virtual address is translated into a 36-bit physical memory address.
8. Pentium II – It was able to process video, audio, and graphics data efficiently by incorporating Intel MMX technology (multimedia data set).
9. Pentium III – It contains SMD (streaming extensions) instructions (SSE) and supports 3D graphics software. It has a maximum CPU clock rate of 1.4 GHz and contained 70 new instructions.
10. Pentium 4 – It implements third-generation address translation that translates a 48-bit virtual memory address to a 48-bit physical memory address. It contains other floating point enhancements for multimedia.
11. Core – It is the first Intel microprocessor with dual-core which is the implementation of 2 processors on a single chip. There is an addition of Visualizing Technology.
12. Core 2 – It extends the architecture to 64 bits and core 2 Quad provides four processors on a single chip. The register set, as well as addressing modes, are 64 bits.

Comparison of major features of X-86 Family:

Microprocessor	8086	80286	80386	80486	Pentium
The data bus (bits)	16	16	32	32	64
Address bus (bits)	20	24	32	32	32
Operating Speed MHz	5 – 10	6 – 20	16 – 33	25- 50	50 – 100
Memory Capacity	1 MB	16 MB	4 GB	4 GB	4 GB
Memory Management	External	External	External	Internal	Internal
PC Type (IBM)	PC – XT	PC – AT	PC – AT	PC – AT	PC – AT
Main Co-Processor	External	External	External	Internal	Internal
Introduction	1978	1982	1985	1989	1993

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