Elektronika MK-52

Years of production: 1983(?) - 11/1991 Display type: 7-segment Price: 115 rubles Display color: Green · · Display technology: Vacuum fluorescent Size: 212mm x 78mm x 35mm Display size: 8+2 digits Weight: 250g · · · · Entry method: Reverse Polish Batteries: 4×"AA" alkaline Advanced functions: trg, exp, log, drg, dms External power: D2-37 Memory functions: n/a I/O: Expansion port · · · · Programming model: Partially merged keystroke Precision: 8 digits Program functions: GOTO, subroutine, conditionals, indirect Memories: 15 Program display: Keycode Program steps: 105 (+512 in EEPROM) Program editing: SST, BST, Overwrite

Elektronika MK-52

The last hurrah for Soviet-designed programmable RPN calculators was the MK-52 made in Kiev around 1986. This machine had 105 program steps capacity, with 512 bytes of internal EEPROM memory for non-volatile storage of programs and data. External modules could also provide additional ROM memory for additional program storage (fabric made). The MK-52 cost 115 rubles, and additional ROM modules containing various programs were another 40 rubles (although the one shown on this page is priced at 16 rubles). This is the only known calculator which used EEPROM for internal storage of program data; most non-volatile storage of the era implemented CMOS memory, or magnetic-cards. Programs and data stored on the MK-52 are lost when the calculator is powered down; however, it is possible to copy both programs and data, up to 512 bytes in total, to internal storage. The internal EEPROM is organized as 1024 4-bit nibbles. Each program step requires 1 byte (2 nibbles) of memory; each register requires 7 bytes (14 nibbles.) When reading, clearing, or writing the EEPROM, the address and range are specified in the form of a 7-digit number, the first digit of which must be non-zero but is otherwise ignored. Address 1aaaann means nn bytes, starting at nibble address aaaa. The D-P switch controls whether data or program memory is transferred; another three-position switch is used to select read, write, and clear (apparently required before write) operations. This machine is functionally equivalent to the MK-61, down to the last EGGOG, er, down to the last bug :-) © Sergei Frolov ROM Module "Dimensions are (WxHxD) (8.25" x 3 1/8" x 1 1/4") It has the green LED 8 digit display and takes 4 AA batteries. I don't see a year stamp on the back, but have the manuals at home that has the original warranty card that is signed and stamped, I believe it's 1983, maybe 1984. It also has a cool clear orange plastic dust cover that goes over the top of the keys. One thing that surprised me was that to enter a number 0 < x < 1 you must type a zero first. For example to enter .25 or 1/4 you can't press (dot) + 2 + 5, you must press 0 + (dot) + 2 + 5. If you leave off the leading zero then it gets entered as 25! It comes in a cheap black plastic case that you can see underneath it in my photograph. Also there are four ports on the back. Two of these ports open up to expose the expansion ports, and the other are permantly shut. I work with a Russian engineer that I believe had one of these, and he said that he used to have some games for them." - Chris Mumford

© Gregory Escov

"I had MK-52 in my own, with ROM cards. I really played some games on it while being a student. I remember some of them "fox hunt" (to find 8 unmovable foxes on field 10x10, quite simple); "flight to Mars" (you can add/decrease acceleration and should land with small speed); "mate black king by knight, bishop and king" (common chess rules and field just small number of figures, MK plays for black king). There were written a lot of such soft for MK-52. All used only 15 registers and < 105 calculator commands. Some games played in real-time mode and used pseudographics like "flight to Mars" did. Both real-time mode and pseudographics are undocumented. I would like to stress that specific feature of B3-34 - MK-52 line was plenty of undocumented features, moreover their number substantially exceeded that of documented ones. I do not know why. Most of them were useful and represented substantial extention of MK-52 documented code. Long before Windows era. :) I never met such amount of undocumented command sequences in western calcs. MK-52 had also at least one bug: built-in MAX function gives zero if one of arguments was zero."

- Leonid Fedichkin

Calculators in Space

Soyuz TM-7, 26 November 1988-27 April 1989

"...and there was a ROM module with astronomical programs that the cosmonauts in Mir used... of course it was military/restricted, and no one ever saw it!"

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