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Electronika BK

From Alfawiki
Electronika BK series
Company typeHome computer series
IndustryComputer hardware
Founded1983
FounderNPO Scientific Center
Headquarters
Soviet Union
Products16-bit home computers compatible with PDP-11 architecture

The Electronika BK series consists of 16-bit home computers compatible with the PDP-11 architecture, developed by NPO Scientific Center under the Elektronika label, which was the Soviet Union’s premier microcomputer design group at the time. This line preceded the introduction of more advanced micros such as the UKNC and DVK models.

Overview

Launched in 1985 after its development in 1983, the BK computers were powered by the К1801ВМ1 CPU, a Soviet-made processor compatible with the LSI-11 architecture. It stood out as the sole Soviet home computer design to receive official government approval for mass production.

With a price tag ranging from 600 to 650 roubles—well above the average monthly Soviet salary of approximately 150 roubles—the BK became widely adopted across the USSR. Its robust CPU combined with a simple design made it particularly popular within the 1990s demoscene. The acronym BK derives from bytovoy kompyuter, which translates to home or domestic computer. These devices were also briefly repurposed as cash registers in locations such as the GUM department store.

Software

The BK was initially delivered as a bare system lacking peripherals and programming utilities. Early software offerings included onboard ROM firmware featuring BASIC and FOCAL interpreters, along with a magnetic tape containing sample programs and diagnostic tests.

Despite partial compatibility with larger professional DVK micros and industrial minicomputers like the SM EVM, its limited memory—typically only 16 KiB accessible out of 32 KiB total—restricted direct software use from more powerful machines. The DVK platform, in contrast, supported expanded memory up to 128 KiB, which facilitated software development beneficial to BK users.

Enthusiasts rapidly adapted tools from DVK and UKNC systems, leading to a flourishing ecosystem of homebrew applications including text editors, databases, operating systems, and games. Many users upgraded their RAM to at least 64 KiB and often incorporated floppy disk controllers, which intensified competition in creating disk operating systems. Although its graphics capabilities were modest, the BK’s capable CPU made it a vibrant platform for gaming and demoscene activities.

Officially, the BK came with OS BK-11—a variant of RT-11—but alternative operating systems such as ANDOS also gained popularity.

Hardware

At its core, the BK employed a 16-bit single-chip K1801VM1 processor running typically at 3 MHz. Overclocking to speeds up to 5 MHz was common, though performance was limited by relatively slow dynamic random-access memory (DRAM). While compatible with Digital Equipment Corporation’s LSI-11 series, it lacked features like the Extended Instruction Set (EIS) and other enhancements. The internal architecture closely mirrored that of the PDP-11. Each unit featured one free expansion slot electrically compatible with Q-Bus, though not mechanically so. Early versions contained 32 KiB of onboard DRAM, half dedicated to video memory; later models expanded this to 128 KiB by adding two 16 KiB video pages.

Video output was managed by the K1801VP1-037 VDC, a simple 600-gate array (ULA) supporting two graphics modes: a high-resolution monochrome mode (512×256) and a low-resolution color mode (256×256 with four colors), including hardware-assisted vertical scrolling. Subsequent models offered sixteen fixed four-color palettes selectable from a 64-color range. Text display was emulated through BIOS routines supporting modes such as 32×25 and 64×25 characters; some operating systems like ANDOS achieved an 80×25 text mode by increasing character density. Video output connected via two separate 5-pin DIN connectors for monochrome or color TV/monitor compatibility. Sound originated from a basic programmable counter linked to an onboard piezoelectric speaker, with the General Instrument AY-3-8910 chip commonly used as an aftermarket sound upgrade.

All BK models incorporated a universal 16-bit parallel port featuring independent input and output lines for peripherals such as printers—though Eastern Bloc printers employed an incompatible IFSP interface requiring adapters for Centronics devices—mice, or Covox-style digital-to-analog converters (DACs) for audio output. A tape recorder interface was also provided for data storage purposes. Later versions included an official floppy disk controller plug-in designed for the Q-Bus slot; this controller was available aftermarket for earlier units as well, with homemade variants frequently adding an additional 16 KiB of memory.

BK-0010

The initial variant, introduced in 1983 with mass production commencing in 1985, incorporated a pseudo-membrane keyboard design—mechanical microswitches beneath a flexible overlay without individual keycaps. It was equipped with 32 KiB of RAM, an 8 KiB BIOS ROM (K1801RE2-017), an 8 KiB ROM containing the FOCAL interpreter (K1801RE2-018), an 8 KiB debugger ROM (K1801RE2-019), one vacant ROM slot, and operated a CPU clocked at 3 MHz. Data storage was primarily handled through tape recorders in the standard factory setup.

This version was often criticized due to its uncomfortable keyboard arrangement—though mechanical, the absence of keycaps resulted in poor tactile response, making it unsuitable for home or educational environments. However, its robust enclosure made it appropriate for industrial controller applications. Other limitations included the default use of the FOCAL programming language instead of the more widely adopted BASIC, along with restricted peripheral support and software options. Despite thorough hardware documentation, it was shipped without any bundled programming utilities.

BK-0010.01

The successor, БК-0010.01 (also noted as -0010-01), preserved the core architecture but introduced a full-travel keyboard and embedded a Vilnius BASIC p-code compiler within ROM, resolving critical issues found in the original model. This BASIC variant was a simplified yet efficient clone of MSX BASIC. Nevertheless, the keyboard still exhibited problems such as key sticking, considerable contact bounce, and accelerated wear; these issues were mitigated in later revisions. The FOCAL interpreter was relocated to an external ROM cartridge designed for the Q-Bus slot.

BK-0010Sh

Focused on educational applications, this version combined either the −0010 or −0010.01 base model with a dedicated current loop network adapter supporting 19200 bits per second (bit/s) data rates via the Q-Bus slot. Utilizing ULA chips K1801VP1-035 and subsequently K1801VP1-065, it accommodated Digital Equipment Corporation (DEC) DL-11 and KL-11 serial interfaces without modem control lines. It was commonly paired with a customized Yunost' compact television monitor tailored for classroom use.

BK-0011

Launched in 1989, the BK-0011 came with 128 KiB RAM organized in 16 KiB segments and featured a CPU running at 4 MHz by default. It incorporated an updated BASIC interpreter stored in ROM and offered 16 selectable video palettes; however, users frequently criticized its unconventional color schemes. A floppy disk controller was included as standard, with disk drives available separately as peripherals.

BK-0011M

Minor revisions introduced in the BK-0011 led to incompatibility with earlier -0010 models, such as inability to load programs from cassette tapes and differences in the sound system. To resolve these issues, the manufacturer redesigned the device into the BK-0011M variant, reinstating backward compatibility; consequently, most BK-0011 units are actually BK-0011Ms. Many enthusiasts upgraded original -0011 machines to meet -0011M specifications.

Mods

Users frequently implemented mechanical switch modifications to improve functionality:

  • Reset push-button: Designed to prevent excessive power cycling caused by worn-out power switches by enabling software-triggered resets; supported by operating systems including ANDOS and MK-DOS.
  • Pause switch: Halts processor instruction execution temporarily, useful for pausing games that lack built-in pause features. Some titles may experience unstable resumption due to ongoing hardware timers. Software-based pause commands are also available.
  • Clock speed switch (commonly called turbo switch): Allows toggling of CPU clock frequency from the standard 3 MHz (BK-0010 series) or 4 MHz (BK-0011 series) up to 6 MHz or down to 3 MHz. Overclocking success depends on individual CPU quality. This modification is typically combined with a pause switch to prevent execution freezes caused by mechanical contact bounce impacting clock signals.
  • Sound on/off or volume control: Adds adjustable volume capability for the internal piezo speaker via a potentiometer; often installed alongside upgraded speakers for enhanced audio output.

More advanced enhancements include hard drive controllers enabling connection of 2.5" HDDs and integration of superior sound chips such as the AY-3-8912 and Covox Speech Thing, significantly broadening multimedia functionality on BK series computers.

Emulators

Multiple software emulators for the BK are available on contemporary IBM PC compatible machines, delivering performance that far exceeds the original device. Moreover, detailed hardware recreations on field-programmable gate array (FPGA) platforms such as the MiST provide precise emulation of the original circuitry.

See also

External links

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