19 bit minicomputing - the Mincal 523 from Dietz

Yes, 19 bits, and core memory, with a parity bit too. That’s 4½ digits, in BCD, and a sign bit. It’s a TTL-built machine from 1971, from Dietz, a German company who first offered the Mincal 3 in 1965.

Sturdy minicomputer with lights and switches

This machine is microcoded, with writeable control store!

The exceptional design of this computer was revealed only little by little during the reverse engineering (there was practically no documentation and all schematics had to be drawn and recreated by hand).
The CPU itself is built simple. The machine consists of a lot of circuit boards with low integrated TTL ICs, three of the boards form the processor control, one contains the ALU and six are for the hardware registers A-F.

Image from this page by the museum at Uni-Stuttgart:
http://computermuseum.informatik.uni-stuttgart.de/dev_en/mincal523/
where you’ll see lots more detail, including pictures of the ROM - magnetics formed in the PCB.
(The museum is open on Tuesdays)

(As seen previously on G+. And with a tenuous connection to Norsk Data, who bought Dietz in the mid-80s, which connection indirectly brought this post to mind when @Tor mentioned ND.)

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