Intel 8008

In April 1972, Intel launched the Intel 8008, the first 8-bit microprocessor in history. This innovation did not come out of nowhere, however. Three years earlier, Computer Terminal Corporation (CTC) was looking for a solution to modernize its Datapoint 2200 terminal. The company contacted Intel, a company founded just one year earlier by Gordon Moore and Robert Noyce, which was limited to memory manufacturing.

CTC had a concrete problem: its terminal used MSI (Medium Scale Integration) components scattered across multiple boards. The idea of concentrating all this logic on a single chip appealed to the company, which named this project with the codename 1201. Stan Mazor and Ted Hoff took charge of the functional specifications before handing over to Federico Faggin and Hal Feeney for the technical implementation.

The architecture faithfully replicated that of the existing CTC processor. An 8-bit accumulator worked with six 8-bit general-purpose registers (B, C, D, E, H, L). The processor handled 14-bit addressing, providing access to 16 KB of memory. Its instruction set remained basic but covered common arithmetic and logical operations, with rudimentary interrupt handling. Technically, approximately 3,500 PMOS transistors etched at 10 microns were packed into an 18-pin package. The clock frequency reached 200 kHz, enabling execution of 60,000 instructions per second.

This 18-pin constraint nearly compromised the project. Intel wanted to control its production costs and refused to increase the number of connections. The design team found itself at a technical impasse, wondering how to pass all the necessary information with so few available connections. The solution came from multiplexing the address and data buses, a technique that complicated usage but made manufacturing economically viable.

The first prototypes came off the production lines in late 1971. Unfortunately, they revealed operational defects. The engineers had to correct the etching masks and restart production. March 1972 finally saw the birth of the first fully functional chips, but CTC had changed its mind in the meantime. The company now considered the 8008 too slow and preferred to develop its own solution in TTL logic.

Intel found itself stuck with a product on its hands but decided to commercialize it. The gamble proved successful. The 8008 found its place in computer terminals, industrial controllers, and scientific instruments. Its launch price—$120 for the standard version, $180 for the fast variant—remained affordable for many designers.

The creation of this processor disrupted the habits of draftsmen who drew the masks by hand on enormous sheets exceeding 1.5 meters in width, at a scale 500 times larger than the actual circuit size. Logic simulations were laboriously performed on the few available mainframe computers in time-sharing mode. The team invented techniques such as bootstrap loads to improve the circuit’s electrical performance.

Intel did not leave its customers to fend for themselves with this unprecedented technology. The company published detailed programming manuals, complete reference documentation, and offered evaluation boards like the SIM-8. These resources enabled engineers to master the microprocessor’s specificities.

Kodak integrated the 8008 into its photocopiers, Toledo Scale into its industrial scales. McDonald’s used it for its first point-of-sale terminals. Some applications continued to use this processor more than ten years after its release. The lack of binary compatibility with subsequent generations like the 8080 explains this loyalty. Rather than reprogramming everything, many preferred to keep their existing developments.

This small component demonstrated that a single chip could house a complete calculator, mass-produced at reasonable cost. Electronic designers began to see things differently. The 8008’s architecture, with its general-purpose registers and bus multiplexing, had a lasting influence on subsequent generations of microprocessors.

Sales remained modest, a few hundred thousand units over its entire commercial career. These figures paled compared to those of the 4004 or the future 8080, but Intel’s management hesitated. It feared becoming a competitor to its own computer manufacturer customers by entering this market too boldly. Texas Instruments attempted to create a rival to the 8008 without succeeding. Ironically, this company filed in 1971 the first patent covering the microprocessor concept, while Intel had only protected certain specific technical aspects of its implementation. A legal battle that illustrated the radical novelty of these technologies.

The lessons from the 8008 directly fed into the design of the 8080. This time, the engineers adopted a 40-pin package that finally gave them the necessary flexibility. They kept the general architecture but improved it considerably in every aspect.

The entire x86 family that dominates the personal computer market retains traces of the 8008. Architectural choices such as byte order (little-endian) or register organization survived fifty years and are found in the most modern processors. As the first 8-bit microprocessor ever commercialized, the 8008 established technical and commercial directions that shaped the semiconductor industry for subsequent decades. Its creation required innovations in methodology and tooling. Despite its technical limitations, it revealed the tremendous potential of microprocessors.