alt Hacker Newshttps://cpu-collection.de/?l0=co&l1=Eastern%20Bloc&l2=DEC%20...
quote:
There were several PDP-11 clones made in Zelenograd near Moscow. Both multi-chip and, later, single chip versions.
Most quantities were 1801VM1 and 1801VM2. Second was much faster (over 10 MHz clock frequency). Both did not have extended addressing and were limited to 64k bytes address space. Later 1801VM3 appeared, containing 22 address extension much like PDP-11/70, but slightly different so original DEC programs could work with only 18 bit (256 kbyte).
These three CPU were not copy of any real chip from DEC. But there was another 5 chip CPU clone of DEC Professional 350. This model was cloned incredibly close, and called "Electronica 85".
The single chip ones were not originally supposed to be PDP-11 compatible - but there was a push to use PDP-11 ISA and Unibus/Qbus in that specific segment, so they reworked the microcode to implement PDP-11 instructions with minimal changes to the chip itself.