4-bit KB1013VK/KB1515HM3 Harvard architecture microcontrollers. These had very limited arithmetics and could only sum.
Elektronika IM
Remember that little silhouetted guy who appeared from nowhere in SSBM, communicated in calculator beeps and confused the hell out of everybody? Yep, the very Mr. Game & Watch, the mascot of the eponymous series of early Nintendo handhelds. Well, he had a brother, who nobody outside of the Iron Curtain has hardly ever seen.
Elektronika IM series was just another of the numerous Soviet clones—this time it's the seminal Nintendo portables that were copied—as rumor has it, after some bigwig in the MIP [1] had seen some during his visit to Japan.[2] The early games were almost literal copies and reconstructed the look-and-feel and gameplay of the Japanese originals very closely, but soon the character begun to be localized: the very second game in the series, Just You Wait! (a copy of Nintendo EG-26 Egg) used Wolf from the eponymous cartoon series, itself a Tom and Jerry clone, and later all sorts of variations of the same theme followed.
What's interesting is that the clamshell design of the later Game & Watch handhelds, the forerunner of Nintendo DS, didn't take off in the Soviet Union—all games in the series featured the same single-leaf case, despite, reportedly, being license-built copies, so it won't really be a problem to acquire the later iteration of the platform, unless the Japanese side walked away from the deal. Also, in the typically confusing Soviet fashion, the same IM index (which means "Игра Микропроцессорная", or Microprocessor Game) was used for several other toys and games that weren't Game & Watch inspired in the slightest—IM-11, for example, which was a clone of the Big Trak toy tank. On the other hand, the IE and I indexes were often used for the G&W clones.
Specifications
65 x 4-bit words on-chip
1830 words on-chip