History of Personal Computers - Introduction - Microprocessor and Cost Reduction

Microprocessor and Cost Reduction

The minicomputer ancestors of the modern personal computer used early integrated circuit (microchip) technology, which reduced size and cost, but they contained no microprocessor. This meant that they were still large and difficult to manufacture just like their mainframe predecessors. After the "computer-on-a-chip" was commercialized, the cost to manufacture a computer system dropped dramatically. The arithmetic, logic, and control functions that previously occupied several costly circuit boards were now available in one integrated circuit, making it possible to produce them in high volume. Concurrently, advances in the development of solid state memory eliminated the bulky, costly, and power-hungry magnetic core memory used in prior generations of computers.

A few researchers at places such as SRI and Xerox PARC were working on computers that a single person could use and that could be connected by fast, versatile networks: not home computers, but personal ones.

After the 1972 introduction of the Intel 4004, microprocessor costs declined rapidly. In 1974 the American electronics magazine Radio-Electronics described the Mark-8 computer kit, based on the Intel 8008 processor. In January of the following year, Popular Electronics magazine published an article describing a kit based on the Intel 8080, a somewhat more powerful and easier to use processor. The Altair 8800 sold remarkably well even though initial memory size was limited to a few hundred bytes and there was no software available. However, the Altair kit was much less costly than an Intel development system of the time and so was purchased by companies interested in developing microprocessor control for their own products. Expansion memory boards and peripherals were soon listed by the original manufacturer, and later by plug compatible manufacturers. The very first Microsoft product was a 4 kilobyte paper tape BASIC interpreter, which allowed users to develop programs in a higher-level language. The alternative was to hand-assemble machine code that could be directly loaded into the microcomputer's memory using a front panel of toggle switches, pushbuttons and LED displays. While the hardware front panel emulated those used by early mainframe and minicomputers, after a very short time I/O through a terminal was the preferred human/machine interface, and front panels became extinct.