The Microprocessor

As in the inventions of the transistor at Bell Laboratories and the planar technology at Fairchild Semiconductor, the next significant development took place in a research environment in which a smaller number of scientists mutually inspired each other in the pursuit of their research goals.

In 1968, Robert N. Noyce, Gordon E. Moore and Andrew S. Grove decided to leave Fairchild Semiconductor and form a new startup company, Intel. With a 1-page business plan, they raised US$ 2.5 million venture capital. In 1970, Intel introduced the 1103, a 4 kbit DRAM, the first high-density semiconductor memory.

In mid-1969, Busicom, a now-defunct Japanese calculator manufacturer, asked Intel to design a set of microchips for a line of high-performance calculators. The specifications provided called for at least twelve chips. Marcian E. Hoff of Intel decided that this solution was to complex and expensive and came up with the concept of a general-purpose information processor.

Figure 3: The Intel 4004

Further refinements led to the design of the Intel 4004, a single-chip microprocessor, released on 15 November 1971. The 4-bit 4004 had 46 instructions, ran at 108 kHz and contained 2,300 transistors in a 16-pin dual in-line package (see Figure 3). Program and data memory were separate, 1K data memory and a 12-bit program counter for 4K program memory (in the form of a 4 level stack, used for CALL and RET instructions). Finally, the 4004 provided sixteen 4-bit (or eight 8-bit) general purpose registers.

The performance of the 4004 had been designed to match the performance of Eniac, the first general-purpose electronic computer (see Figure 4) constructed using during World War II using approximately 19,000 vacuum tubes10).

The performance of the 4004 is estimated at 0.06 MIPS. From its inception in 1971, the microprocessor has grown exponentially in performance and complexity according to the predictions in Moore's law. By comparison, the Intel Pentium Pro (1995) is a 200 MHz chip with 5.5 million transistors and a performance of 428 MIPS.

As a general-purpose device, the microprocessor impacted electronic systems design severely. Since the early 1970's, a wide variety of electronic products have been realized using standard microprocessors. Unfortunately, the general-purposeness of microprocessors implied that not all electronic systems could reach the full potential of technology.

Figure 4: The Eniac 1. U.S. Army Photo

Author: Flemming Stassen