Elektronika MS 0511 / UK-NC / USSR personal microcomputer

«Elektronika MS 0511» «UK-NC» — personal microcomputer, USSR educational computer.
Set: monoblock with network card, SCART cable and 4-drive emulator.
Fully functional.

Main technical characteristics:
Central processor (CPU): 16-bit KM1801VM2, clock frequency 8 MHz, performance - about 600 thousand op/s
Peripheral processor (PPU): 16-bit KM1801VM2, clock frequency 6,25 MHz, performance - about 400 thousand op/s
CPU Memory: RAM — 64 KB, available to user - 56 KB
PPU Memory: RAM — 32 KB, available to user — 22 KB, ROM — 32 KB
Video RAM — 96 KB / 3 blocks, 32 KB each
Video modes: text 24 lines of 10/20/40/80 characters (character matrix - 8×11 dots), graphic - 640 × 288 (lower horizontal resolution is provided by scaling by 2, 4 or 8 times, which can be applied separately to each line), 8 colors per line (from a palette of 16). Also 2 additional service lines are displayed.
Keyboard: "Elektronika MS 7007", 88 keys
Dimensions: "Electronica MS 0511" - 448 × 290 × 80 mm
Weight: 3.5 kg
Power consumption: no more than 25 W

The KM1801VM2 instruction set is the PDP-11 instruction set, with extended arithmetic instructions (MUL, DIV, ASH, ASHC). Floating-point arithmetic instructions (FADD, FSUB, FMUL, FDIV) are implemented in software.

Interfaces:
- Two video outputs (connected in parallel)
- Parallel port for connecting a printer and other devices via IRPR, IRPR-M (Centronics) interfaces
- The serial port "Styk S2" is a functional analogue of RS-232, with a fixed exchange rate of 9600 bits/s
- Interface for connecting a household tape recorder (exchange rate - 1200 bit/s)
- Edge 60-pin connector for connecting devices via the MPI protocol to the CPU bus. Almost the only device was a network adapter:
The network adapter is based on the KR1801VP1-065 integrated circuit. The local area network is a two-wire ring network, 57,600 bits/s, with parity control, the network address 1..63 was set by switches on the adapter board; it is serviced by the MC.SYS driver.
- Two 48-pin connectors for connecting various peripheral devices to the PP bus, including:
NGMD controller - KMD UK device (U13.065.013) based on the KR1801VP1-097 or -128 BIS (serviced by the MZ.SYS driver)
electronic disk (there were versions with a capacity of 128 KB, 512 KB and 1 MB)
- various ROM cassettes with interpreters for programming languages BASIC, Focal, etc.

Peculiarities:
The UKNC's special feature is its dual-line architecture with two identical KM1801VM2 processors. The central processor performs tasks defined by the user's programs, and the peripheral processor performs the logical functions of the input-output device controllers (keyboard, display, etc.), but it can also be used to run user tasks. A high-speed byte parallel interface for exchanging commands and data is installed between the CPU and PP buses. In addition, register access to the CPU RAM is organized from the PP bus to transfer data arrays between the buses while the CPU is running. A similar architecture is used in the DVK with a color graphic display controller (CGDC).
Another feature of the UKNC is the organization of video memory into three 32 KB plans with access via registers. The number of plans used determines the number of colors displayed simultaneously: from 2 to 8 (out of a possible 16). Register access eliminates the need to allocate the main address space for video memory, but slows down the operation. To speed up the operation, it is possible to use directly addressed RAM as video memory. At the same time, unused video memory plans can be used to store data, for example, by organizing a virtual disk.