Electronika BK

Электроника БК-0010 is the first model (originally released in 1983, the serial production since mid-1984). It has a pseudo-membrane keyboard (an array of mechanical microswitches without keycaps, covered by flexible overlay), 32 KiB RAM, 8 KiB ROM with BIOS (chip K1801RE2-017), 8 KiB ROM with FOCAL interpreter (K1801RE2-018), 8 KiB ROM with debugger (K1801RE2-019) and one free ROM slot, and its CPU is clocked at 3 MHz. A tape recorder is used for data storage in the factory configuration.

This model was criticized for its uncomfortable keyboard – while mechanical in nature, lack of keycaps lead to the same unsatisfactory tactile response, that was seen as unacceptable when the machine was used in home or educational settings, although such keyboard could be easily sealed completely, so this version found widespread use as an industrial controller. Other points of criticism included the archaic FOCAL programming language supplied by default and the complete lack of peripherals and software. While all hardware was well documented and easy to work with, the machine was delivered without any programming tools.

The follow-up version, БК-0010.01 (sometimes referred to as -0010-01), is essentially the same machine, but with a conventional full-travel keyboard and a Vilnius BASIC p-code compiler in the ROM, correcting the weakest points of its predecessor. While the BASIC dialect used is quite powerful and well-optimized (it is actually a somewhat scaled-down clone of MSX BASIC), the keyboard is a mixed blessing. While it is much more comfortable to work with, its quality left much to be desired, and the keys were prone to sticking, significant bounce and wore quickly, though a model with a further improved keyboard became available later. The FOCAL interpreter was not dropped but instead shipped on an external ROM cartridge that could be inserted into the Q-Bus slot.

Электроника БК-0010Ш is a model intended specially for school use. It can be either the −0010 or −0010.01 model but was supplied with a special current loop network adapter rated at 19200 bps, which can be inserted into the Q-Bus slot. Based on ULA chip K1801VP1-035 (and later on K1801VP1-065), the adapter is compatible to DEC DL-11 and KL-11 serial interfaces, but without modem control bits. It also includes a monitor (usually a modified Yunost' compact TV), since in school setting it couldn't be expected to be connected to household TV.

BK-0011 was released in 1989. It has 128 KiB of RAM divided into 16 KiB pages, its CPU is clocked at 4 MHz by default; it includes a newer version of BASIC in ROM and 16 selectable video palettes, which were almost universally criticized by users for their odd color combinations. It has a floppy controller, but the drive was still sold separately.

BK 0011M

Some changes in the BK-0011, while minor, made it incompatible with earlier -0010 models. In particular, it can not load 0010 programs from a cassette tape. Even if it could have loaded them, crucial subsystems, such as sound, are still incompatible. Public outcry forced the manufacturer to redesign the machine, restoring compatibility with earlier models. The resulting model, the BK-0011M, quickly went into production, and most BK-0011 series computers are actually BK-0011Ms. Since the modifications were minor, most of the handful of -0011 models that made it to market were upgraded to -0011M models by enthusiasts.

It was not uncommon among owners to install one or two mechanical switches that made using the computer more convenient. Some of the common mods were:

• Reset button. Programs often hung. Also, some games did not have a properly implemented Exit function. Without this button, the computer had to be reset by power cycling, which eventually led to a worn out power switch on the external power supply. The reset interrupt can be caught by the operating system, so under such systems (for example, ANDOS, MK-DOS), the reset button exits to the OS's file manager.
• Pause switch. This switch activated hardware suspension of instruction execution in the processor. The pause switch was useful for pausing games, most of which did not have a pause key. A few games, however, did not behave gracefully after being returned from suspension, because the programmable hardware timer built into the processor chip is still running while the instruction execution was suspended. The BK also has a software key combination for pause.
• Clock speed switch ("turbo" switch). This changes the processor clock speed from the standard 3 MHz (BK-0010* series) to 4 or 6 MHz, or from the standard 4 MHz (BK-0011* series) to 3 or 6 MHz. Not all processor samples work reliably at 6 MHz; the possibility of such overclocking has to be determined experimentally for each sample. Switching the clock speed changes the pace of dynamic games. The turbo switch usually has to be installed together with the pause switch, because the simplest circuit for switching the clock speed produces bad shapes in the clock signal due to contact bounce when the mechanical switch was flipped, running the risk of hanging the software execution unless the processor is in the suspended state.
• Sound on/off switch, or sound volume knob, which adjusts the volume level of the internal piezoelectric speaker using a potentiometer. At this same time as adding this, the modder can replace the speaker with a louder one.

These modifications are relatively simple and can be carried out by users who knew how to handle a soldering iron. Most of the people in the program sales cottage industry can also do the mods for a small fee. Enthusiasts also managed to connect more advanced devices to BK series computers: they developed a hard disk controller, and 2.5" HDDs were successfully used with BK computers. Other popular enhancements are AY-3-8912 sound chips and Covox Speech Thing.