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The Radio-86RK (russian: Радио-86РК) is a build-it-yourself home computer designed in the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...
. It was featured in the popular ''Radio'' (russian: Радио) magazine for
radio ham An amateur radio operator is someone who uses equipment at an amateur radio station to engage in two-way personal communications with other amateur operators on radio frequencies assigned to the amateur radio service. Amateur radio operators ha ...
s and electronics hobbyists in 1986. The letters RK in the title stands for the words ''Radio ham's Computer'' (russian: Радиолюбительский компьютер). Design of the computer was published in a series of articles describing its logical structure, electrical circuitry, drawings of printed circuit boards and firmware. The computer could be built entirely out of standard off-the-shelf parts. Later it was also available in a kit form as well as fully assembled form.


Predecessors

The Radio-86RK is the successor of earlier build-it-yourself computer of the same designers, the
Micro-80 The Micro-80 (russian: Микро-80) was the first do-it-yourself home computer in the Soviet Union. Overview Schematics and information were published in the local DIY electronic magazine ''Radio'' in 1983. It was complex, using an KR580VM80A- ...
, and has limited compatibility with it. Its description was also published in a series of articles in the ''Radio'' magazine in the early 1980s. But its complex design, consisting of several modules and containing about 200 chips, lack of printed circuit board drawings and most importantly lack of chips on sale made the assembly of the computer hard to accomplish. ''Micro-80'' computers were assembled by only a few enthusiasts.


Assembly process

To assemble the computer, it was required to acquire the necessary
electronic component An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are no ...
s, to make two
printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...
s and mount all components on them. It was mostly a single board computer, as the second board served only as the base to mount the keyboard keys. The main board used a single large connector for power, keyboard, tape recorder and even video output. Hence it was easy to disconnect the board and work on both sides of it outside the case. Next, the
firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...
has to be written in two erasable ROM chips using a chip programmer. Also a
power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As ...
unit, a
keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Mu ...
and a computer case were to be made. The computer used a normal domestic TV set connected to a
composite video Composite video is an analog video signal format that carries standard-definition video (typically at 525 lines or 625 lines) as a single channel. Video information is encoded on one channel, unlike the higher-quality S-Video (two channe ...
input as a display. As most Soviet TVs of the time did not have video inputs, it was necessary to install a special module or modify the TV's electronics to implement it. The approximate cost of all required components was about 260
ruble The ruble (American English) or rouble (Commonwealth English) (; rus, рубль, p=rublʲ) is the currency unit of Belarus and Russia. Historically, it was the currency of the Russian Empire and of the Soviet Union. , currencies named ''rub ...
s. The circuitry of the Radio-86RK contains only 29 chips and was relatively easy to assemble. However, finding the chips to buy was difficult, as they were scarce and sold in small volumes in major cities of the USSR. It was particularly difficult to find the KR580VG75 video chip, which was produced only in small quantities. This led to the development of a replacement video circuit which contained 19 chips on a separate board, and was similar to the display module of the Micro-80 computer. The editorial board of ''Radio'' magazine received a large amount of mail in response to the publication. In almost every letter, readers noted how difficult it was to find the necessary electronic components. The editorial board published an appeal to the Soviet electronics industry, proposing they begin producing Radio-86RK kits commercially. By the end of the 1980s manufacturing of computer cases, keyboards and main boards for the Radio-86RK, as well as selling electronic components were carried out by numerous cooperatives.


Technical specifications

*
CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
: KR580VM80A (
Intel 8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier 8008 design, although without binary compatibil ...
A clone, until mid-1983 was designated as KR580IK80A) clocked at 1.777 MHz. For simplicity's sake the clock generator KR580GF24 (Intel 8224 clone) is used both for CPU and video controller. As 16 MHz clock generator frequency is chosen to generate television compatible signal, the CPU is unable to run at its maximum speed of 2.5 MHz. *
RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...
: 16
KiB The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
in original version, using K565RU3A chips (4116 clone). It is possible to double memory size by mounting additional RAM chips on top of the chips installed on the main board. * ROM: 2
KiB The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
erasable ROM of type K573RF5 (2716 clone), contains
monitor Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, West ...
firmware * Video controller: KR580VG75 programmable CRT controller, interfaced with KR580VT57 (
Intel 8257 The Intel 8257 is a direct memory access Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). Without DMA, when the C ...
clone)
DMA DMA may refer to: Arts * DMA (magazine), ''DMA'' (magazine), a defunct dance music magazine * Dallas Museum of Art, an art museum in Texas, US * Danish Music Awards, an award show held in Denmark * BT Digital Music Awards, an annual event in the U ...
controller. The DMA controller is also used for dynamic memory refresh. Video controller KR580VG75 is a clone of
Intel 8275 The Intel 8085 ("''eighty-eighty-five''") is an 8-bit microprocessor produced by Intel and introduced in March 1976. It is software-binary compatible with the more-famous Intel 8080 with only two minor instructions added to support its added in ...
, a rare chip not used in any mainstream system, and originally proposed for terminals. ** Text mode: 64 x 25 characters, monochrome. Images for the upper case Cyrillic and Latin characters in KOI-7 N2 encoding are stored in the KR573RF1 (2708 clone) erasable ROM. ** Semigraphics: 2 x 2 dot matrix combinations in the graphic character subset – 128 x 50 dots total. Higher resolutions are available by appropriate video controller programming. * Keyboard: 66 keys. The keyboard matrix is attached via programmable peripheral interface chip KR580VV55 (
Intel 8255 The Intel 8255 (or i8255) Programmable Peripheral Interface (PPI) chip was developed and manufactured by Intel in the first half of the 1970s for the Intel 8080 microprocessor. The 8255 provides 24 parallel input/output lines with a variety of pr ...
clone) and scanned by CPU. * Sound: CPU pin INTE used as a sound source. This pin is usually used to interface with programmable interrupt controller, but since the computer did not have any interrupt sources, the pin was used for sound generation. CPU commands EI and DI allowed switching the pin state. * Storage media: cassette tape. With DMA controller turned on the CPU is unable to measure time intervals precisely, that is required for tape reading and recording. Therefore, during tape operations, the DMA controller turns off. This results in stopping the video controller and memory refresh, so the CPU performs memory refresh programmatically. Signal from recorder is amplified by the К140УД6 (analog of MC1456), negative part is cut away by diode and then the signal is fed to the dedicated TTL input of the same KR580VV55 that serves the keyboard. * Recording format: 0 was written as a pair of values 0,1 and 1 was written as 1,0. Hence the overall signal had no constant component and could be stored within the frequency range supported by the tape recorder. A synchronization byte (E6) was written first to synchronize the reading frame. A simple second layer that featured leading zeroes, offset, length and checksum was implemented on the top. * Additional I/O: The computer also has a slot for the second chip of the same type. This second chip is meant for various specific projects (amateur radio constructions, consumer electronics controllers, sensors, etc). As long as only the keyboard and tape recorder are required, this second chip does not need to be mounted on the circuit board. * Address space: the address space consists of 8 large slots, addressing 8 Kb each. Two or four of them are dedicated for RAM (so 16 or 32 Kb), one for ROM and DMA controller (during write operations, ROM is disconnected from the bus, and data is transferred to the DMA controller; during read operations, DMA controller is disconnected from the bus, and data is transferred from the ROM), one for video controller and two for the interface chips, main and optional. Only RAM actually uses all available addresses, IO devices only use a few cells within they dedicated 8 Kb segment. Separate IO commands that Intel 8080 has are not supported. * Stripboards: to give more creative possibilities for amateurs, the main board has the two small
stripboard Stripboard is the generic name for a widely used type of electronics prototyping material for circuit boards characterized by a pre-formed regular (rectangular) grid of holes, with wide parallel strips of copper cladding running in one direct ...
s next to the main connector.


Software

The only software available to the user after turning on the computer is a monitor contained in ROM. The monitor supports basic debugging functions, it allows viewing and modifying memory cells, loading and saving memory contents to the tape, entering and running programs in binary code. The monitor is also
HAL HAL may refer to: Aviation * Halali Airport (IATA airport code: HAL) Halali, Oshikoto, Namibia * Hawaiian Airlines (ICAO airline code: HAL) * HAL Airport, Bangalore, India * Hindustan Aeronautics Limited an Indian aerospace manufacturer of figh ...
: programs that access the hardware only by calling the monitor library support both 16Kb and 32 Kb RAM versions and often also Micro-80 predecessor. Initially, the ''Radio'' magazine distributed programs for the Radio-86RK in the form of hexadecimal dumps. After entering the program dump into the computer's memory, it could be saved to the tape. It was easy to make a mistake when typing in large dumps, so the magazine published
checksum A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify data ...
s along with the dumps. It was necessary to execute "O" monitor directive to calculate the checksum. The magazine published two versions of the
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
interpreter: an adapted version of ''Micro-80'' BASIC and a version specially developed for the Radio-86RK featuring enhanced editing capabilities, new functions, and other improvements. Other software published in the magazine included
assembler Assembler may refer to: Arts and media * Nobukazu Takemura, avant-garde electronic musician, stage name Assembler * Assemblers, a fictional race in the ''Star Wars'' universe * Assemblers, an alternative name of the superhero group Champions of ...
,
debugger A debugger or debugging tool is a computer program used to test and debug other programs (the "target" program). The main use of a debugger is to run the target program under controlled conditions that permit the programmer to track its executi ...
,
disassembler A disassembler is a computer program that translates machine language into assembly language—the inverse operation to that of an assembler. A disassembler differs from a decompiler, which targets a high-level language rather than an assembly ...
,
text editor A text editor is a type of computer program that edits plain text. Such programs are sometimes known as "notepad" software (e.g. Windows Notepad). Text editors are provided with operating systems and software development packages, and can be ...
, voice recorder, music editing system. Also, a lot of BASIC programs were published, including calculations for electronic circuits design and games. Another way of obtaining software was the tape exchange among Radio-86RK owners. In 1988, the law on cooperation in the USSR came into force, which made legal to produce software for profit by individuals and cooperatives. From that moment it became possible to buy software for the Radio-86RK.


Operating systems

In 1989 the RAMDOS
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
was developed for the computer. It uses part of computer's RAM as a
RAM drive Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...
. The contents of RAM drive can be loaded and saved to the tape. The operating system has a minimalistic user interface with only seven commands; it also adds support for file operations to the BASIC interpreter. In October 1992, the ''Radio'' magazine and ''TOO Lianozovo'' company announced a
floppy-disk controller A floppy-disk controller (FDC) has evolved from a discrete set of components on one or more circuit boards to a special-purpose integrated circuit (IC or "chip") or a component thereof. An FDC directs and controls reading from and writing to a ...
for the Radio-86RK and the Microsha. The disk operating system (DOS) was stored in erasable ROM on the controller board. The ''Radio'' magazine published only the electrical circuitry of the controller but not the firmware. Radio-86RK owners were invited to buy the fully assembled controller or a kit along with two floppy disks containing external DOS commands, programming languages and text description of the operating system.


Industrial made versions

The first industrially produced version of the Radio-86RK was the computer named ''Microsha'' (an abbreviation for the words ''Microcomputer'' and ''School''). Initially, the authors had given that name to the original computer, but the editorial board has changed the name to Radio-86RK. Eventually, the name ''Microsha'' was given to the industrially produced version of Radio-86RK. ''Microsha'' preparation for serial production went in parallel with Radio-86RK articles publication. The changes authors made to the design and firmware made ''Microsha'' incompatible with Radio-86RK. In 1989, the ''Radio'' magazine had published new firmware for ''Microsha'' that improved software compatibility. Following magazine publication, a number of factories started industrial production of several home computer models using the Radio-86RK design. Not all models were fully compatible with Radio-86RK and included different improvements, such as expanded memory size, additional character sets, rudimentary color support. The list of models includes: * Alfa-BK * Impulse * Microsha * Electronica KR-01, Electronica KR-02, Electronica KR-03, Electronica KR-04 (electronic kits) * Partner 01.01 * Spektr-001 * Apogey BK-01 * Krista * UMPK-R-32 * Sogdiana-1 * Mikro-88 Volume of production for a number of models:


Successors

The technical capabilities of the Radio-86RK were very modest. It did not have a graphics mode. The RAM expansion was impossible without serious modifications and loss of compatibility. As the volume of production of home computers was small, and the demand for them kept increasing, the editorial board decided to publish a new design for the build-it-yourself computer. Although the designers of the Radio-86RK had developed a new 16-bit computer, the Micro-16 (based on the
K1810VM86 The K1810VM86 (russian: К1810ВМ86, italic=yes) is a Soviet 16-bit microprocessor, a clone of the Intel 8086 CPU with which it is binary and pin compatible. It was developed between 1982 and 1985. The original K1810VM86 supported a clock frequen ...
microprocessor, with a CGA-compatible graphics mode that was capable of running software for the
CP/M-86 CP/M-86 was a version of the CP/M operating system that Digital Research (DR) made for the Intel 8086 and Intel 8088. The system commands are the same as in CP/M-80. Executable files used the relocatable .CMD file format. Digital Research als ...
and
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few o ...
), the editorial board again opted for a computer based on the 8-bit processor KR580VM80. The main reason for this was the availability of electronic components for purchase and their cost. The publication of articles on the new computer Orion-128 began in January 1990.


References


External links


Radio-86RK (Russia)
The Centre for Computing History. *
Radio-86RK emulator written in JavaScript



skiselev / radio-86rk
— modern redesign of the Radio-86RK as a single board. {{List of Soviet computer systems Home computers Soviet computer systems