Evolution of microprocessors

The years of development of microprocessors are divided into five generations.

      1.The First Generation (1971-73)

Intel's 8008

Intel corporation introduced 4004, the first microprocessor in 1971. it is evolved from the development effort designing a calculator chip.

There were three other processors in the market during the same period:

• Rockwell international's PPS-4 (4 bits)
• Intel's 8008 (8 bits)



National Semiconductor's IMP-16
Image source: www.antiquetech.com

• National Semiconductor's IMP-16 (16 bits)

They were fabricated using P-MOS(P-channel Metal Oxide Semiconductor) technology which provided low cost, slow speed and low output currents. They were not compatible with Transistor-Transistor Logic(TTL).

      2. The Second Generation (1974-78)

Intel's 8085
Image source: www.cpu-world.com

This generation marked the beginning of very efficient 8-bit microprocessors. Some of the popular processors were:

• Motorola's 6800 and 6809
• Intel's 8085
• Zilog's Z80

They were manufactured using N-MOS(N-channel Metal Oxide Semiconductor) technology. This technology offered faster speed and higher density than P-MOS. It is Transistor-Transistor Logic(TTL) compatible.

      3. The Third Generation (1979-80)

Intel's 8086
Image source: www.old-computers.com

This age was dominated by 16-bits microprocessors.

Some of them were:

• Intel's 8086/80186/80286
• Motorolla's 68000/68010

They were designed using H-MOS(High-Speed MOS implies both a short channel between source and drain, and also design (layout) rules that deal with minimum feature size of less than two micrometers) . H-MOS provides some advantages over N-MOS as :

- speed-power-product of H-MOS is four times better than that of N-MOS.

- H-MOS can accomodate twice the circuit density compared to N-MOS.

Intel used H-MOS technology to recreate 8085A and named it as 8085AH with a higher price tag.

      4. The Fourth Generation (1981-95)

Intel's 80386

• This era marked the beginning of 32 bit microprocessors.
• Intel introduced 432, which turned out a bit problematic.
• Then a clean 80386 was launched.
• Motorolla introduced 68020/ 68030.

They were fabricated using low-power version of H-MOS technology called HC-MOS. Motorolla introduced 32-bit RISC(Reduced Instruction Set Computing) processors called MC88100.

      5. The Fifth Generation (1995-Till date)

This age's emphasis is on introducing chips that carry on-chip functionalities and improvements in the speed of memory and input devices along with introduction of 64-bit microprocessors.

Intel leads the show here with Pentium, Celeron and recent dual and quad core like processors working with upto 3.5 GHz speed.