The Intel 4004, launched on November 15, 1971, holds a significant place in computing history as the first commercially available microprocessor. This 4-bit central processing unit (CPU), developed by Intel, marked a pivotal moment, transitioning from specialized computing components to a single-chip solution. Initially conceived for a calculator, its potential quickly expanded, leading to its marketing for general-purpose computing. The 4004's introduction
was a technological and economic milestone, setting the stage for future advancements in integrated electronics.
Genesis and Initial Design
The development of the Intel 4004 was rooted in a project for Busicom, a Japanese calculator manufacturer. The initial design for Busicom's calculator architecture involved seven chips, with three dedicated to a specialized CPU function. Ted Hoff, head of Intel's Application Research department, proposed a simplified architecture using only four chips, integrating the CPU into a single chip. This idea, along with an instruction set formulated with his assistant Stanley Mazor, was accepted by Busicom in October 1969. However, neither Hoff nor Mazor were chip designers, and the project was subsequently transferred to the MOS department, led by Les Vadasz.
The project faced delays until Federico Faggin was hired by Intel in April 1970 as project leader and chip designer. Faggin, with the assistance of Busicom's logic designer Shima, who had no prior chip design experience but was eager to learn, completed the project in a record nine months. The 4004 became fully functional by mid-March 1971. Faggin then convinced Intel management to introduce the chip to the broader market, despite its original exclusive design for Busicom. Busicom agreed to Intel using the CPU in non-calculator systems in exchange for a reduction in the cost of the MCS-4 family chips. This agreement paved the way for Intel's public announcement of the 4004 in November 1971, under the slogan "Announcing a new era of integrated electronics."
Technical Characteristics and Production
The Intel 4004 was a 4-bit microprocessor, part of the MCS-4 family, which also included memory and input/output circuits designed to create a complete computer system. The 4004 itself was composed of approximately 2,300 transistors, utilizing PMOS logic and a 10 µm structure width. It operated at a clock frequency ranging from 500 to 740 kHz, with eight cycles per instruction. The chip was housed in a 16-pin dual in-line package (DIP) and featured a data-address space of 5120 bits, based on a Harvard architecture.
Its instruction set comprised 46 commands. The processor included 16 registers, each 4 bits wide, which could also be configured as eight 8-bit registers. It supported subroutine calls with CALL and RET commands, utilizing a stack capable of holding up to four return addresses. Unlike contemporary microprocessors, the 4004 also managed memory and I/O bus control, functions typically handled externally. This integration meant the 4004 was not only a complete CPU but also incorporated additional functionalities not usually considered part of a CPU's role. Production of the 4004 continued until 1981, and its design was succeeded by the Intel 4040 in 1974. In 2006, 35 years after its release, Intel made the schematics available for non-commercial use.
