SAPO

Also called SAmočinný POčítač.Designed by doc. Antonín Svoboda.It was manufactured from 1957 by Ústav matematických strojů.

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The first Czechoslovak digital computer was the SAPO, which was based on relay technology, as no other suitable components were available in Czechoslovakia at the time. The computer worked until 1961, when it was destroyed by a fire in one relay block. Input and output of information was ensured by punched labels. A magnetic drum unit (constructed by Václav Chlouba) with a capacity of 1024 words served as memory.

Architecture

The computer architecture was binary using floating point, word length was 32 bits and instructions had five addresses. The first two addresses were operand addresses. The third address was for the result and the last two addresses were pointers to the next instruction depending on the sign of the result. The execution speed of all instructions was the same and was approximately 3 operations per second (op/s).

Fault tolerance

Due to the low reliability of approximately 7,000 relays and 400 vacuum tubes, triple modular redundancy was chosen in the design of the computer. The correct result was ensured by a majority vote. This procedure eliminated any single error, assuming the computer was programmed correctly. It was the world's first fault-tolerant computer.

References

Golan, P. Marcela Efmertová and Tomáš Konečný, (2019). Czechoslovak Computer School. HISTELCON. https://doi.org/10.1109/HISTELCON47851.2019.9040026
https://historiepocitacu.cz/samocinny-pocitac-sapo.html (WebArchive)

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