KC 85
Encyclopedia
The KC 85 were models of microcomputer
s built in East Germany, first in 1984 by Robotron
(the KC 85/1
) and later by VEB Mikroelektronik "Wilhelm Pieck
" Mühlhausen (KC 85/2, KC 85/3 and KC 85/4).
Due to huge demand by industrial, educational as well as military institutions, KC 85 systems were virtually unavailable for sale to smaller customers.
They were based on the U880
CPU
(an East German clone of the Z80
), with clock speeds of 1.75 and 2 MHz.
There were two main lines in the KC 85 series, the KC 85/2 (project name HC 900) to /4 and the KC 85/1
(project name Z 9001) by Robotron
, which was a different system (only the CPU
and the name were the same, but later the format of saving the programs on tape cassettes and the BASIC were also made compatible). In 1989, VEB Mikroelektronik Mühlhausen came up with the KC compact, but due to the GDR collapse very few units got actually produced and sold and — being a CPC
clone — it was a KC in name only; thus it is usually not counted among the KC family.
Unlike the Pravetz series 8
personal computers, manufactured in Bulgaria
, which were equipped with decent dedicated displays, floppy discs and good quality keyboards, the entire series used a TV set for a monitor (by standard TV-HF via coaxial cable
, FBAS (roughly composite video) or RGB) and a standard tape recorder as data storage. The keyboards were of low quality. The KC 85/1 used an integrated calculator-style keyboard with small "keys" of hard plastics, while KC 85/2-4 used a separate keyboard driven by a remote control IC.
The KC 85/2 was the first computer made in Mühlhausen and had only font ROMs for capital letters, and no BASIC in ROM.
Then, the KC 85/3 was introduced and this one had a BASIC
interpreter in ROM
, freeing the user from having to load the BASIC interpreter from a cassette every time. Both systems typically had 16 KB of RAM, but could be expanded with add-on modules. (The module sockets feature prominently on photos, as they occupy the upper 50% of the casing nearly completely.)
The KC 85/4 had 64 KB of RAM (not counting the luxurious video ram of more than 40 KB) and better graphics capabilities.
All KC-series computers from Mühlhausen were able to display graphics at a resolution of 320×256 pixels. But the color possibilities were not that good (each 4×8-pixel cell had a single foreground (out of 16) and background color (out of 8, slightly darker than foreground equivalents). This limitation was brought down to 1×8 on the KC 85/4, which also featured a reasonable video RAM addressing mode and a special 4-color mode which could color every pixel independently. The colors were not paletted in any KC before the KC compact. There was no "text mode", everything had to be painted; this and the awkward video RAM layout and suboptimal ROM code made the KC 85/2-3 rather slow at printing and scrolling (improved very much on KC 85/4).
There were no blitter
s, and the video subsystem was hand-brewed (the KC compact used a 6845 as the CPC did of course). Sound and tape output was implemented by CTC
channels driving flipflops. Memory bank-switching was common since the total address space was only 64 KB. When running Mühlhausen's BASIC, the video RAM (at 0x8000) was banked in only during video operations, thus the maximum BASIC free RAM was about 47 KB instead of 32 KB. The module extension system also used bank-switching and made it theoretically possible to extend to megabytes of RAM (even more modules could be used by adding expansion devices, yielding sort of a tower), however neither BASIC nor most of the applications were prepared to use this as free space.
The KC 87
was a better KC 85/1 with BASIC also in ROM. There was a color option (the 85/1 was only monochrome), but no real graphics apart from ROM pseudographic characters.
The wiring diagrams were openly available and there were also a lot of different (and often home-made) schemes and hardware parts. Various magazines published programs and hardware diagrams and also instructions on how to build them.
and BASIC (the KC 85/2 had to load BASIC from tape), but it was possible to use various modules (sold by VEB Mikroelektronik Mühlhausen) or load software from tape, thus allowing programming in Forth and Pascal
. The operating system was CAOS ("Cassette Aided Operating System"). It was a simple monitor where one could run different "system services" like LOAD (load a program), JUMP (into extension module ROM), MODIFY (memory cells) or BASIC (if it had been built into the ROM or had been loaded from tape). New commands could be added to the menu by magic numbers (standard:
In the last years of the GDR, a floppy attachment ("tower"-style, too) was produced. It featured a 4 MHz CPU and a 5¼" Floppy drive
(you could have up to four of them). These (literally: the U 880 A in the attachment did) were able to run CP/M
, which was called MicroDOS. (One had to JUMP from the base system to the floppy system and boot from a floppy - another CAOS or MicroDOS). There was also a disk extension mode for CAOS.
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
s built in East Germany, first in 1984 by Robotron
Robotron
VEB Kombinat Robotron was the biggest East German electronics manufacturer. It was based in Dresden and employed 68,000 people . It produced personal computers, SM EVM minicomputers, the ESER mainframe computers, several computer peripherals as well as home computers, radios and television...
(the KC 85/1
Robotron KC 87
The Robotron KC 87, fully known as the Kleincomputer robotron KC 87 , was an 8-bit home computer released in 1987 and produced in East Germany by the VEB Robotron-Meßelektronik "Otto Schön" Dresden, part of the Kombinat Robotron...
) and later by VEB Mikroelektronik "Wilhelm Pieck
Wilhelm Pieck
Friedrich Wilhelm Reinhold Pieck was a German politician and a Communist. In 1949, he became the first President of the German Democratic Republic, an office abolished upon his death. He was succeeded by Walter Ulbricht, who served as Chairman of the Council of States.-Biography:Pieck was born to...
" Mühlhausen (KC 85/2, KC 85/3 and KC 85/4).
Due to huge demand by industrial, educational as well as military institutions, KC 85 systems were virtually unavailable for sale to smaller customers.
Technical information
U880
The U880 was an 8-bit microprocessor manufactured in the German Democratic Republic. It was manufactured in NMOS logic technology and encased in a DIL40 package....
CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
(an East German clone of the Z80
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
), with clock speeds of 1.75 and 2 MHz.
There were two main lines in the KC 85 series, the KC 85/2 (project name HC 900) to /4 and the KC 85/1
Robotron KC 87
The Robotron KC 87, fully known as the Kleincomputer robotron KC 87 , was an 8-bit home computer released in 1987 and produced in East Germany by the VEB Robotron-Meßelektronik "Otto Schön" Dresden, part of the Kombinat Robotron...
(project name Z 9001) by Robotron
Robotron
VEB Kombinat Robotron was the biggest East German electronics manufacturer. It was based in Dresden and employed 68,000 people . It produced personal computers, SM EVM minicomputers, the ESER mainframe computers, several computer peripherals as well as home computers, radios and television...
, which was a different system (only the CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
and the name were the same, but later the format of saving the programs on tape cassettes and the BASIC were also made compatible). In 1989, VEB Mikroelektronik Mühlhausen came up with the KC compact, but due to the GDR collapse very few units got actually produced and sold and — being a CPC
Amstrad CPC
The Amstrad CPC is a series of 8-bit home computers produced by Amstrad between 1984 and 1990. It was designed to compete in the mid-1980s home computer market dominated by the Commodore 64 and the Sinclair ZX Spectrum, where it successfully established itself primarily in the United Kingdom,...
clone — it was a KC in name only; thus it is usually not counted among the KC family.
Unlike the Pravetz series 8
Pravetz series 8
Pravetz were Bulgarian computers, manufactured mainly in the town of Pravetz but also components and software were produced in Stara Zagora, Plovdiv and other.- History :...
personal computers, manufactured in Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
, which were equipped with decent dedicated displays, floppy discs and good quality keyboards, the entire series used a TV set for a monitor (by standard TV-HF via coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
, FBAS (roughly composite video) or RGB) and a standard tape recorder as data storage. The keyboards were of low quality. The KC 85/1 used an integrated calculator-style keyboard with small "keys" of hard plastics, while KC 85/2-4 used a separate keyboard driven by a remote control IC.
The KC 85/2 was the first computer made in Mühlhausen and had only font ROMs for capital letters, and no BASIC in ROM.
Then, the KC 85/3 was introduced and this one had a BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
interpreter in ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
, freeing the user from having to load the BASIC interpreter from a cassette every time. Both systems typically had 16 KB of RAM, but could be expanded with add-on modules. (The module sockets feature prominently on photos, as they occupy the upper 50% of the casing nearly completely.)
The KC 85/4 had 64 KB of RAM (not counting the luxurious video ram of more than 40 KB) and better graphics capabilities.
All KC-series computers from Mühlhausen were able to display graphics at a resolution of 320×256 pixels. But the color possibilities were not that good (each 4×8-pixel cell had a single foreground (out of 16) and background color (out of 8, slightly darker than foreground equivalents). This limitation was brought down to 1×8 on the KC 85/4, which also featured a reasonable video RAM addressing mode and a special 4-color mode which could color every pixel independently. The colors were not paletted in any KC before the KC compact. There was no "text mode", everything had to be painted; this and the awkward video RAM layout and suboptimal ROM code made the KC 85/2-3 rather slow at printing and scrolling (improved very much on KC 85/4).
There were no blitter
Blitter
In a computer system, a blitter is a circuit, sometimes as a coprocessor or a logic block on a microprocessor, that is dedicated to the rapid movement and modification of data within that computer's memory...
s, and the video subsystem was hand-brewed (the KC compact used a 6845 as the CPC did of course). Sound and tape output was implemented by CTC
CTC
-Government bodies:* Calcutta Tramways Company* California Commission on Teacher Credentialing* Canadian Tourism Commission* Counter-Terrorism Committee * Counterterrorism Center or CTIC-Educational institutes:* Central Texas College...
channels driving flipflops. Memory bank-switching was common since the total address space was only 64 KB. When running Mühlhausen's BASIC, the video RAM (at 0x8000) was banked in only during video operations, thus the maximum BASIC free RAM was about 47 KB instead of 32 KB. The module extension system also used bank-switching and made it theoretically possible to extend to megabytes of RAM (even more modules could be used by adding expansion devices, yielding sort of a tower), however neither BASIC nor most of the applications were prepared to use this as free space.
The KC 87
Robotron KC 87
The Robotron KC 87, fully known as the Kleincomputer robotron KC 87 , was an 8-bit home computer released in 1987 and produced in East Germany by the VEB Robotron-Meßelektronik "Otto Schön" Dresden, part of the Kombinat Robotron...
was a better KC 85/1 with BASIC also in ROM. There was a color option (the 85/1 was only monochrome), but no real graphics apart from ROM pseudographic characters.
The wiring diagrams were openly available and there were also a lot of different (and often home-made) schemes and hardware parts. Various magazines published programs and hardware diagrams and also instructions on how to build them.
Programming languages
The KC 85 could be programmed in assembly languageAssembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
and BASIC (the KC 85/2 had to load BASIC from tape), but it was possible to use various modules (sold by VEB Mikroelektronik Mühlhausen) or load software from tape, thus allowing programming in Forth and Pascal
Pascal (programming language)
Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal...
. The operating system was CAOS ("Cassette Aided Operating System"). It was a simple monitor where one could run different "system services" like LOAD (load a program), JUMP (into extension module ROM), MODIFY (memory cells) or BASIC (if it had been built into the ROM or had been loaded from tape). New commands could be added to the menu by magic numbers (standard:
7F 7F 'commandname' 01) anywhere in the memory space.In the last years of the GDR, a floppy attachment ("tower"-style, too) was produced. It featured a 4 MHz CPU and a 5¼" Floppy drive
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
(you could have up to four of them). These (literally: the U 880 A in the attachment did) were able to run CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
, which was called MicroDOS. (One had to JUMP from the base system to the floppy system and boot from a floppy - another CAOS or MicroDOS). There was also a disk extension mode for CAOS.
Hobby projects
There were a lot of different projects for the KC 85:- a new keyboard (The original being extremely poorly manufactured)
- RAM diskRAM diskA RAM disk or RAM drive is a block of RAM that a computer's software is treating as if the memory were a disk drive...
- interfaces (V.24RS-232In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
and others) - text systems; WordPro actually featured 80 characters per line mode (4×8 font)
- connection to electronic typewriters (like the GDR-product "Erika S 3004") as keyboard and printer (but dot matrix emulation was very slow)
- programming language BASICODEBASICODEBASICODE was a computer project intended to create a unified standard for the BASIC programming language. BASIC was available on many popular home computers, but there were countless variants that were mostly incompatible with each other...
(a special BASIC dialect); BASICODE-programs were even broadcast by radio