After the integrated circuit, the only place to go was down - in size, that is. Large scale integration (LSI) could fit hundreds of components onto one chip. By the 1980's, very large scale integration (VLSI) squeezed hundreds of thousands of components onto a chip. The ability to fit so much onto an area about half the size of a U.S. dime helped diminish the size and price of computers. It also increased their power, efficiency and reliability. Marcian Hoff invented a device which could replace several of the components of earlier computers, the microprocessor. The microprocessor is the characteristic of fourth generation computers, capable of performing all of the functions of a computer's central processing unit. The reduced size, reduced cost, and increased speed of the microprocessor led to the creation of the first personal computers. Until now computers had been the almost exclusively the domain of universities, business and government. In 1976, Steve Jobs and Steve Wozniak built the Apple II, the first personal computer in a garage in California. Then, in 1981, IBM introduced its first personal computer. The personal computer was such a revolutionary concept and was expected to have such an impact on society that in 1982, "Time" magazine dedicated its annual "Man of the Year Issue" to the computer. The other feature of the microprocessor is its versatility. Whereas previously the integrated circuit had had to be manufactured to fit a special purpose, now one microprocessor could be manufactured and then programmed to meet any number of demands. Soon everyday household items such as microwave ovens, television sets and automobiles with electronic fuel injection incorporated microprocessors. The 1980's saw an expansion in computer use in all three arenas as clones of the IBM PC made the personal computer even more affordable. The number of personal computers in use more than doubled from 2 million in 1981 to 5.5 million in 1982. Ten years later, 65 million PCs were being used. Computers continued their trend toward a smaller size, working their way down from desktop to laptop computers (which could fit inside a briefcase) to palmtop (able to fit inside a breast pocket).
Fourth Generation Integrated Circuits
And a close-up...
Control Data Intebrid Fourth Generation IC's
Intel 8086 CPU
The Intel 8086 was based on the design of the Intel 8080 and Intel 8085, with a similar register set, but was expanded to 16 bits. It featured four 16-bit general registers, which could also be accessed as eight 8-bit registers, and four 16-bit index registers (including the stack pointer). The segment registers allowed the CPU to access 1 meg of memory. The 8086 was not considered a masterpiece, many of its features were extremely obtuse.
Intel Pentium CPU
Intel's superscalar successor to the 486 was introduced on March 22,1993. It has two 32-bit 486-type integer pipelines with dependency checking. It can execute a maximum of two instructions per cycle. It does pipelined floating-point and performs branch prediction. It has 16 kilobytes of on-chip cache, a 64-bit memory interface, 8 32-bit general-purpose registers and 8 80-bit floating-point registers. It is built from 3.3 million transistors on a 262.4 square mm die with ~2.3 million transistors in the core logic. Its clock rate is 66MHz, heat dissipation is 16W. In burst mode, the Pentium loads 256 bits of data into its 16K on-board cache in one clock cycleIt is called "Pentium" because it is the fifth in the 80x86 line. It would have been called the 80586 had a US court not ruled that you can't trademark a number. The successors are the Pentium Pro and Pentium II. A floating-point division bug was discovered in October 1994.
