(I've edited this question to include a second board - the seller told me he had two of the same, but having received the photo of the second board it's clear to me that they're different).

I am in the process of buying a Soviet Elektronika EVM S5 21, which is billed on some Russian-language sites as "the first Soviet microcomputer". The seller is also offering the pictured unidentified circuit boards. I have tried Googling the serial number of the first board but to no avail, and my knowledge of electronics in general and Soviet electronics in particular means I have no idea what it is or what its function is. The second board has several integrated circuits though it's hard from the photo to read the serial numbers. The one component serial number I can read with confidence 284КН1Д (284KN1D) only shows up in a Russian Google search for its precious metal content, which is sadly the only reason most people are interested in Soviet electronics these days. In a transliterated search there is mention of a UHF module, so maybe the second board is some sort of monitor/television interface?

So my question is: does anyone here recognise these boards in particular, or if not can anyone say what the general purposes of these boards likely are? Might they be of some use as peripherals to the S5 21?

Unidentified Soviet circuit board

Second Unidentified Soviet circuit board

  • 2
    Are there any interface connections on the right side of the board? Some peripherals are listed in ru.wikipedia.org/wiki/Электроника_С5#Модули_С5-21
    – Leo B.
    May 17, 2023 at 16:21
  • 2
    A bunch of 6- or 8-pin devices in TO cans, could be logic ICs or analog devices. The number of caps (and whatever the red boxes are) could mean almost anything...
    – Jon Custer
    May 17, 2023 at 18:28
  • 1
    The S5-21 was microprocessor based, so much is true, but all digital boards used bus connectors somewhat similar to VG style, not card edge like shown above. Also, being late 1970s, it was already based on DIP/QIP style chips, not TO. So either the board is from some secondary device, an older iteration (there were S5 implementations prior to the 21), or something unrelated.
    – Raffzahn
    May 17, 2023 at 20:14
  • 1
    Sometimes it helps to prepend К (cyrillic) to the IC numbers (packaging type/radiation hardness), and/or to drop the last letter (quality class). 284КН1 is an AC/DC switch.
    – Leo B.
    May 17, 2023 at 23:33
  • 2
    Yeah, it is "284КН1А", the last letter is А, not Д. eandc.ru/catalog/detail.php?ID=683
    – tum_
    May 18, 2023 at 8:39

1 Answer 1


Looking at the Russian Wikipedia for the EVM S5-21, the specs are quite good:

Microcomputer based on a single-chip 16-bit N-MOP microprocessor K586VM1 (old name K586IK1). The developer of the microprocessor is A. V. Palagin.

  • Processor "Electronics MS2716". Processor K586VM1.
  • Bit depth - 16 bits
  • The number of basic commands is 31, the command system is the same for the Electronics S5 family
  • Clock frequency - 2 MHz
  • Speed ​​- approximately 200 thousand register-register commands per second
  • 16 general purpose registers for each of 16 tasks
  • Addressable memory - 32K 16-bit words (64 KB)
  • Built-in RAM - 512 bytes (four K586RU1 chips with a capacity of 256 4-bit words each)
  • Built-in ROM - 4096 bytes (two K586RE1 chips with a capacity of 1024 16-bit words, 350 ns access time)
  • 64 parallel channels, four K586BB1 chips, each with a tunable 8-bit structure and two 8-bit I/O channels
  • Eight K155IE7 chips forming a frequency grid
  • Power consumption - no more than 20 W

The processor can execute the “core” of 16 instructions in hardware, the remaining 15 instructions are executed in firmware. Total number of teams with modifications - 256

The processor module "Electronics S5-21" contains two MPI channels , the first channel is used for communication with local input-output devices, and the second one is used for machine-to-machine communication in multiprocessor complexes and for communication with shared devices.

Also looking at the photo of board, this is several generations ahead of the two boards in your question.

So definitely not a peripheral, and I'd assume they come from a much earlier, totally unrelated system, if they are cards from a computer at all.

From the integration density, the first one looks similar to the Flip Chip modules that made up the earlier PDP minicomputers.

Since you wrote in the comments "only going for the S5 21 board": The Russian Wikipedia also mentions the main parallel interface (MPI), and on the page for that states:

The main parallel interface ( MPI ) is a standard that defines a set of lines and procedures for exchanging a processor and peripheral modules inside a computer using a combined (multiplex) address and data bus. The standard provides for an exchange rate of up to 5.6 MB / s with a transmitted data width of 8 or 16 bits and an address width of 16 to 24 bits and was focused on use in systems of low and medium performance. The requirements of the standard are set out in OST 11.305.903-80 and GOST 26765.51-86.

Electronics S5 computers , starting with Electronics S5-21, use the MPI as a bus for communicating with external devices. The Elektronika S5-21 model has two separate MPI channels: one for communication with local devices, the second for organizing machine-to-machine communication and connecting shared external devices when organizing multi-machine complexes. Connector - GRPMSh-1-61.

It also lists the signals. If these are the external connectors of your board, you'll probably need a digital signal analyzer to make sense of the signals (in particular if they are trying to read from external ROM during boot), and then you'll need something to simulate the missing cards. Quite a project.

  • Ok I'm accepting your answer, and only going for the S5 21 board. The next challenge will be getting it to communicate with the outside world! One side has cables to peripherals, all cut, and the seller has no idea what happened to them.
    – harlandski
    May 19, 2023 at 3:28
  • @harlandski The Russian wiki page also lists "interface modules", among them a teletype module, which shouldn't be so hard to communicate with, and a display module, which probably will be pretty hard. And if you just got the main board, and not the computer itself, you'll probably also need to figure out power supply, which can be challenge.
    – dirkt
    May 19, 2023 at 5:07
  • @harlandski might be also worth trying to find a group of Russian retro-enthusiasts, and asking them if they can dig up some manual. Unless you speak Russian, searching for those is no fun...
    – dirkt
    May 19, 2023 at 5:08
  • I do speak Russian, and I've found a sort of user's manual for the whole S5 series, which I need to dig into. I've done some googling for the peripherals but with little success so far.
    – harlandski
    May 19, 2023 at 6:44

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