The Mark-8 microcomputer holds a significant place in the history of personal computing as one of the earliest do-it-yourself microcomputer kits available to hobbyists. Introduced in 1974, it predated more famous systems like the Altair 8800 and helped spark the microcomputer revolution of the 1970s.
The Mark-8 was designed by Jonathan A. Titus, a graduate student in chemistry at Virginia Polytechnic Institute and State University (commonly known as Virginia Tech). Titus, who had a background in electronics and engineering interests, became fascinated with the potential of microprocessors after learning about the Intel 8008 CPU. As a student, he saw the opportunity to create an affordable computing device that individuals could build and experiment with at home. His goal was to make computing accessible beyond large institutions and corporations.
In early 1974, Titus developed the Mark-8 using the Intel 8008 microprocessor, which had been released in 1972. The design was simple yet innovative for its time, focusing on a kit that enthusiasts could assemble themselves. Rather than selling a complete computer, Titus offered printed circuit boards (PCBs) and construction plans, requiring builders to source the components separately.
The project gained widespread attention when it was featured on the cover of the July 1974 issue of Radio-Electronics magazine. The article, titled "Build the Mark-8: Your Own Minicomputer," provided detailed schematics, assembly instructions, and parts lists. This publication is often credited with inspiring a generation of hobbyists and engineers to explore microcomputing. Titus sold the set of six PCBs for $50, and over 500 sets were reportedly sold, though many more people likely built versions from the magazine plans.
The Mark-8 was based on the Intel 8008, an 8-bit microprocessor running at approximately 0.5 MHz. It featured:
The system consisted of six circuit boards housed in a chassis about the size of a large breadbox. It had no built-in storage, keyboard, or display; programs were entered manually via switches, and results were read from LEDs. Power requirements were modest, drawing from a standard power supply. The total cost to build one, including parts, was around $120-$150 in 1974 dollars.
Building the Mark-8 was not for the faint-hearted. It required soldering skills, debugging, and patience, as there was no operating system or high-level programming language initially. Users programmed in machine code or assembly. Despite these limitations, the Mark-8 demonstrated the feasibility of personal microcomputers. It included innovative features like memory expansion ports and the ability to interface with teletype machines or other devices, paving the way for more advanced systems.
While not as commercially successful as the later Altair 8800, the Mark-8 is recognized as one of the first microcomputer kits and a precursor to the home computer era. It inspired user groups, such as the Mark-8 Users Group, where enthusiasts shared programs and modifications. Titus went on to co-found the company Personal Computing Inc. and contributed to other early computing projects.
Today, surviving Mark-8 units are rare and valuable collector's items, often fetching thousands of dollars at auctions. The Smithsonian Institution holds one in its collection, assembled by Titus himself. The Mark-8 symbolizes the DIY spirit that fueled the personal computer revolution, proving that computing power could be democratized.