In the 1950s, computer engineers fought against a long list of limitations, some of which still affect us today, starting with miniaturization and power consumption. Any idea of portability required solutions that seem extreme now, and a perfect example is the DYSEAC, a computer built by the National Bureau of Standards (the current US NIST). The beast was so large and heavy that it used two trailers, yet its construction was revolutionary for its time.
The Osborne 1 weighed 10.7 kilograms. The Compaq Portable came in at 13 kilograms. Both machines hit the market less than two years apart and caused a real earthquake. Today they are little more than museum pieces, but if anyone wants to criticize their portability, they definitely were not the worst. The story takes us to mid-June 1950, when the National Bureau of Standards switched on SEAC, the Standards Eastern Automatic Computer. Even though it occupied a large part of a room, SEAC was a "small" system with 747 vacuum tubes and a weight of only 1.5 tons. While SEAC began its operations, the Bureau was already working on a superior version for the United States Army Signal Corps. Its name was DYSEAC… and it occupied two trailers.
A report from 1961 on the main computer systems, published by the Ballistic Research Laboratories, states that DYSEAC needed two trailers. Both were filled with the control console, input/output, central module, storage, power supplies, and a huge air conditioning system split into two. The full configuration of DYSEAC, including 900 vacuum tubes, the mercury delay line memory (Delay Line Memory, 512 words of 45 bits each) and more than 24,000 diodes, reached 20 tons.
Innovations and Legacy
Beyond its size and weight, DYSEAC is remembered for two remarkable details: it was one of the first computers to incorporate PCBs into its design, and in 1956 it was connected to SEAC so both could work together on a single problem, much like a cluster. Over time, DYSEAC was replaced by MOBIDIC, which cut the trailers down to one by using transistors… but that is another story.
