Atlas (computer)

The Atlas was one of the world's first supercomputers. It operated from 1962 until 1972. This machine was so massive in its capability that a famous saying emerged. People claimed that if Atlas went offline, half of the United Kingdom's total computer capacity was lost.

As a second-generation computer, it utilized discrete germanium transistors. These components allowed it to perform much faster than previous generations of technology. The Atlas was not just a machine; it was a landmark in computing history.

The most significant breakthrough of the Atlas was its use of virtual memory. At the time, engineers called this concept a "one-level store." It used a specific technique known as paging to manage data. Paging allowed the computer to use more memory than was physically present in its core store. The system integrated 16K words of core store with 96K words of drum store. This was achieved by treating the drum store as an extension of the main memory. This approach was revolutionary and eventually became a standard feature in almost all modern computers.

To manage these complex tasks, the Atlas relied on a sophisticated operating system called the Supervisor. Building this software required a massive effort by a team of programmers. Led by David Howarth, the team produced 35,000 lines of assembler language. This software enabled multiprogramming, which allowed the machine to handle many different tasks at once. This was essential because the computer needed to coordinate various peripheral devices. Without the Supervisor, the central processing unit (CPU) would waste time waiting for data from slow devices like card readers.

The development of Atlas began as a response to American computing progress. In the mid-1950s, the United Kingdom realized it was falling behind the United States. Tom Kilburn's team at the University of Manchester began experimenting with transistor-based systems in 1956. They initially named their design MUSE, which stood for "microsecond engine." This name reflected a goal to perform one instruction every microsecond. Eventually, the project became a joint effort between the University of Manchester, Ferranti, and Plessey. Ferranti received a grant of £300,000 from the National Research Development Corporation to build the system.

Several different versions of the Atlas were installed in various locations. The first machine was officially commissioned on December 7, 1962. A second, very large installation was built at the Atlas Computer Laboratory near Oxford. This version contained 48 kWords of 48-bit core memory and 32 tape drives. Ferranti also developed a derivative system for the University of Cambridge. This machine was called Titan, or Atlas 2, and featured a different memory organization. Other Atlas 2 machines were delivered to the CAD Centre and the Atomic Weapons Research Establishment.

In terms of raw power, Atlas was a true leader of its era. While American machines like IBM STRETCH were slightly faster, Atlas was much faster than the Univac LARC. For example, Atlas could add two floating-point numbers in about 1.59 microseconds. The STRETCH machine completed the same task in 1.38 to 1.5 microseconds. Despite this, experts claimed Atlas was the most powerful system because of how it handled large sets of jobs. By the mid-1960s, the original Manchester machine was running on a schedule of 20 hours per day. During this time, it might run as many as 1,000 different programs.

The legacy of the Atlas continues to influence the field of computer science. Its invention of virtual memory is recognized as a major milestone by organizations like the IEEE. Even the design of later machines was influenced by the Atlas. The CDC 6600, which eventually surpassed the Atlas, was developed using ideas from the original MUSE design. Today, pieces of this history are preserved for future generations. National Museums Scotland holds parts of the Chilton Atlas in Edinburgh. The main control console was rediscovered in 2014 and is now at the Rutherford Appleton Laboratory.