M-3 drum memories

M-3 drum memory, 4KB
M-3 drum memory, 8KB

In 1956, the Hungarian Academy of Sciences created the Cybernetics Research Group, which was responsible for the marketing and development of the domestic computer technology.

The first Hungarian vacuum tube computer, the M3 was built based on Soviet documentation. The MTA KKCs started the work in 1957 with many young engineers and mathematicians, among whom several became renowned personalities of the computer field in Hungary. The original Soviet design was significantly reworked, and modified to fit Hungarian component supply possibilities.

The capacity of the first magnetic drum was initially 1 Kword (31 bit/word - 4 KB) and that was increased to 1,6 Kword, later another magnetic drum was connected to it so the full capacity increased to 3,2 Kword. The writing of the data and the readback was carried out through 8 read/write head units with 5 tracks each, at a speed of approximately 50 words/second. In the course of further developments, a 1 Kword (= 4 KB) capacity ferrite core memory unit was connected to it as well, by which its operating speed increased to 1000 operations/second. At the beginning, a Siemens 5 track punched tape Teletype served for data entry and writing. Later it was changed to a fast FACIT 8 track punched tape reader and a Creed puncher. In the machine, 2500 vacuum tubes operated altogether, with an electrical consumption of 10 kW and MTBF 7-8 hours.

It had no operation systems, the commands had to be written in machine codes. It had in total 500 subunit and 1000 vacuum tubes of which 20 had to be replaced daily due to the rapid wear and tear. The memory was a robust, nearly 1 m tall structure, of which up to four could be connected to the machine instead of the original Soviet one. As a consequence of the development, the drum memory was later replaced by the ferrit core which allowed faster execution of the operations.