The MRB Z1013 (Mikrorechnerbausatz = microcomputer kit) was an East German Single-board computer produced by VEB Robotron Riesa which was primarily intended for private use and educational institutions. It was powered by a U880 processor (a Z80 clone) and sold together with a membrane (flat foil) keyboard. Initially, the kit was equipped with 16-KByte DRAM, which was later replaced by a 64-KByte version.
The kits first became available for sale in 1985 and were distributed in a unique way at the time. To purchase, buyers had to send a postcard to the Robotron shop in Erfurt and wait six to 12 months to pick the kits up personally.
The package contained the assembled and tested motherboard, a membrane keyboard, various small parts and detailed technical documentation. This basic kit was shipped without a power supply or casing for the PCB. Most users tended to program the kit using the BASIC interpreter, which was loadable from a compact cassette or by using a ROM cartridge. The BASIC interpreter contained a common core binary, which was identical across home computer models. So the programs were widely compatible among different models of GDR-manufactured computers despite differences in capabilities.
Robotron was also the manufacturer of another line of computers, the Z9001, KC85/1 and KC87, which shared some of the same expansion modules – offering more options also for Z1013.
The system bus connector was based on the K1520 standard for 8-bit computers in the GDR. This conformity to one standard across computers, ranging from tank-sized mini computers to small home computers, allowed the reuse of hardware from minicomputers with the same bus interface. This meant that most of the hardware and binary code from one platform could be used across very different platforms and allowed the sharing of resources.
This groundbreaking standardization was due to the need for common standards and compatibility between computer users in the Eastern Bloc.
Opinion is divided over the widespread use and popularity of the MRB Z1013 in the GDR. With a total of 25,000 kits sold over its lifetime (from 1985 to mid-1990), it fared well in comparison to other models. However, some analysts put this success down to the relative ease of access to the kits compared to other computer offerings.
After all, the key point for the success was the simplistic makeup down to a bare minimum. It is still debatable if it repelled potential users or actually lead to a higher productions volume. Either which way, demand and production kept a kind of balance. To this extent, it was the only computer freely available for private purchase.
== History ==
Despite the Cold War and the associated high-technology embargo CoCom the government pushed for an ambitious program to keep up with international development of engineering and microelectronics. That generated a huge interest among individuals who tried to develop electronics at work or at home aside from the government's economic programs. In 1984 the first two lines of home computers the Z9001 and HC900 were presented to the public. Due to small scale of production those devices were difficult to obtain. They were very expensive, but still could not satisfy the demand.
With a production yield of a few percent, a significant amount of circuits failed to pass the acceptance criteria. The components were called "Anfalltyp" or "rejects". Most of them were functional, but exceed allowed tolerances. Within limits, e.g. speed or access time, they may work fine. Therefore, the manufacturing companies pushed for a development of simple fault-tolerant learning or hobby computers which can make use of the rejects. The use of waste production could lower the reported reject rates and partly close gap in demand for home computers.Following the same concept to sell rejects as a fraction of the original price, the computer design should only consist of the cheapest and easiest available circuits. As a result, three single board computers were brought to industrial production: the LC80 with calculator display and keyboard, the Polycomputer 880 with 8-digit seven-segment display and the more comfortable Z1013 with TV output.The initiators of the Z1013 concept favored a caseless single-board computer with membrane keyboard. Through simple appearance and design the price had been kept under 1000 M for the targeted group of electronics amateurs. The development and production transferred to the well-established industry PCB manufacturer VEB Robotron Riesa in early 1984.
=== Development ===
The state planning targets for the mostly young engineers and employees of the corresponding group of developers ("youth research collective") of the VEB Robotron Riesa foresaw an expandable single board computer with a minimum of material and manufacturing costs. To reduce production costs, the device was designed as a kit without a housing whose prefabricated assemblies were end-mounted by the user.
The computer had to use home electronics such as televisions and tape recorders present in East-German households.The narrow specifications with respect to the low production costs while using inferior electronics components and the demand for largely compatible interfaces and software of the Robotron small computer Z 9001 and KC 85/1 was only limited by a system architecture realized that at the most affordable and field-proven 8-bit microprocessor U880 together with standardized electronic wiring blocks at significantly reduced system clock.
Full-fledged graphics and interfaces for specific peripherals fell victim to cost pressure. However, the conception of the computer as a modular system saw the possibility of connecting additional peripherals, such as the expansion of memory by also being developed expansion modules before.Development work began in mid-1985. The first prototype with a memory of 16 kilobytes (KB) and membrane keyboard was presented to the responsible authorities in the fall of 1985 and started after its acceptance with the planning and preparations for series production, which lasted until November 1985. Because of the 'reject type' components to be used, the system clock was reduced from the 2 MHz usual in home computers to 1 MHz for higher reliability.
=== Z1013.01 and Z1013.12 ===
The first batch of 150 kits with 16 KB memory went into production in December 1985. These were available at the end of the year exclusively on pre-order in the shop for home electronics of VEB Robotron Erfurt and in a shop of the state-owned Handelsorganisation (HO) in Riesa for 650M. In addition to the image output device and a tape recorder by the user an appropriately sized power supply was also to provide and to solder the connecting cable for the keyboard on the computer board before commissioning. The single-board computer was officially presented to a wider audience for the first time at the Leipzig Spring Fair in 1986.In addition to the supply of the home computer market by 1987, a few kits with the designation Z1013.12 were manufactured for the industrial sector. It used regular "typed" circuits, an increased system clock of 2 MHz and 1 KB of static RAM as main memory.
Robotron developed additional components for internal usage, like a pixel graphic extension or a battery-backed 4KB memory. Even though those were not available via the official Robotron sales channel, the goal was provide that information as reference or enable independent reuse.
Despite extensive tests and multi-stage multi-day duration tests in production the installed reject types often led to disturbances and thus to complaints from users. The economic disadvantages due to the elaborate test procedures and subsequent repairs could no longer be outweighed by the reasonable price of used defective components and led to a rethinking by the person responsible. Production from July 1987 was changed to use in acceptably prices regular components sold as Z1013.16 .
=== Z1013.16 and Z1013.64 ===
Since the differences between reject types and regular circuits limited only to their reliability, in 1987 decided to change the kits only regular components could without major changes to the board and are therefore made cost-saving. In addition to increased reliability of the produced from 1987 variant Z1013.16 also has a higher system clock of 2 MHz, which is equivalent to a doubling of computing power. In addition, the system software has been supplemented by appropriate program components for use with a much more comfortable block keyboard with 58 keys. Users of the older kits were according to procurement of components and the modified operating system also upgrade their systems with the aid of a soldering iron. 
An important aspect of revaluations made is - apart from the improved reliability - with the appropriate upgrade of memory producing the broadest compatibility of Z 1013.16 with minicomputers Z 9001, KC 85/1 and KC 87 In addition to the associated utilization of other software also stood their expansion modules, for example, to upgrade the memory, now the Z-1013-users. 
Through the interim relaxation of the CoCom embargo, falling prices in late 1988 was added a more modernized version of the Z-1013 series. This Z 1013.64 with 64 KB of memory was made until production ceased in mid-1990. 
=== Modern replicas ===
The simple and manageable architecture of the system, extensive documentation of the manufacturer and not least the free usage of the system software enable miniaturized replica of the Z 1013 with today's technical means, with a manageable effort. Such modern realization was the first time in 2013 - as well as other home computer systems - as an implementation of a programmable logic circuit (FPGA) in addition to embedded systems. The simulation using FPGA technology was initially intended only as a technical feasibility study, but in retrospect also their practical utility to the test. Due to the miniaturization and the possibility of battery operation, it is an easily stowable, reliably operating and portable alternative to the original schonenswerten technique
== Technical Details ==
The Robotron fully assembled printed circuit board contains the CPU, the RAM and read-only memory, screen control and multiple peripheral connections. The main board measured 215 mm x 230 mm 80 mm x 160 mm with the keyboard together with connection cables, various small parts and documentation.
=== CPU ===
The system architecture is based on the U880 microprocessor, an unauthorized replica of the Z80 microprocessor from Zilog. The Z1013.01 models were clocked with only 1 MHz as they used circuits which had passed limited quality criteria("reject types"). For the other models, fully qualified types like the 2 MHz U880 microprocessor were used. 
The CPU has access to a 64K address range, where by design 59 KB are available RAM for program use. To workaround that limits bank switching concepts or external RAM-discs has been used.
=== Memory allocation, RAM, ROM, and interfaces ===
The memory that is addressable by the CPU is segmented into regions for the system software, freely usable memory, pluggable extensions and the graphics memory. The system software often referred to simply as the "machine language monitor" is either flashed on a 2KB or 4KB ROM chip, depending on the computer model. The memory addresses for the system software range from $ F000 to $ F7FF or $ FFFF respectively. After power on the system software also uses the memory between $0000 and $0100 to store various variables, so this space should not be used by the user either.
The addresses of the freely usable memory (nearly 16KB) range from $0100 to $3FFF on the Z 1013.1 and the Z 1013.6 and can go up to $E000 if the system has been expanded with 16 KB RAM modules. The 64KB version Z 1013.64 further extends the memory range up to $EC00 where the video memory starts and takes up the address space to $EFFF. For programming of the computer the desired programming language, such as Tiny BASIC 87 with 3 KB or the significantly larger KC 87 BASIC with 10 KB, must be loaded into memory from cassette or added via a plug-in cartridge. Loading Tiny Basic from cassette for example reduces the freely available memory for writing BASIC programs to about 12 KB In the basic configuration with 16 KB RAM, so that a memory upgrade is recommended for larger programming projects. Is the programming language loaded from a plug-in module the usable memory at Z1013.01 and Z1013.16 does not change, though. 
For connecting peripherals to computers are equipped with a cassette interface and a user port (a built-in U855-PIO). These units are, in the case of Z1013.01 also to reject types. For expansion, there is a slot ("Bus Expansion") ready. 
=== Graphics, input and output ===
For the output of the computer graphics include factory only a character generator, the text or graphic symbols (in "quasi Graphics") with a 32 × 32 characters with 8 × 8 pixels can represent. The needed for this to ROM located fixed character set contains 96 alphanumeric and control characters and graphic symbols 146.  A pixel graphics mode ("graphic") is by default not available, but can be supplemented in DIY. For instructions were published in various magazines and books until the early 1990s. The black-and-white image is output through the coaxial RF antenna port on a standard TV, the backfitting of color representation are possible. The operation of the keyboard and the control of the tape recorder via the built-in computers input and output port U855-PIO (English Parallel Input Output).
== Peripherals and extensions ==
In addition to the products sold by Robotron extensions are countless more, many of which were presented in printed publications.
=== Mass storage ===
In connection with mainly western home computers of the 1980s came mainly for data backup tape recorders and floppy drives also, in a professional environment with the personal computers increasingly hard - and removable disk drives used. The cheapest version of the data recording by compact cassette has the disadvantage of low data transfer rates and so long loading times, whereas the much faster and more reliable disks and disk drives were much more expensive to purchase, or in the case of the GDR were hardly available. Upon publication of the Z 1013 for data recording were merely tape recorder and tape systems available. Ports for connecting disk drives did not come until the reunification period on.
==== Cassette recorder ====
The Z-1013 computer equipped ex works with a cassette interface for storing programs and data on compact cassette by a standard cassette recorder with prescribed in the manual minimum requirements for contact configurations and the frequency response . Frequently used here were small-scale devices, such as the types Geracord, Datacord and later LCR-C DATA manufacturer VEB Elektronik Gera.
==== Floppy systems ====
A disk system 1013 was never intended by the developers of the Robotron-Z because of his hobby character and therefore its low economic priority, especially appropriate control electronics had to be imported until 1987 and that was expensive to purchase. With the publication of the circuit produced in the GDR U8272, a replica of the Intel developed floppy disk controller P8272A, suggestions and basic procedures for building your own floppy systems for the DDR home computers were also published.  The predominant in the GDR lack especially in the field of drive mechanisms are ordered and thus the construction of a floppy disk system for the economically insignificant Z 1013 made almost impossible, so building instructions were published until the reunification period. 
In the magazine amateur radio in mid-1992 a simple hardware interface along with listing was Disk Monitor presented for the operation of the Commodore 1541-II floppy with the Z 1013. There are up to four disk drives can be connected each with a capacity of 170 KB per disk side. The recording format is compatible with the Commodore computer so that data from both systems are easily interchangeable. 
=== Chassis and power supply module ===
The computers are used only for processing simple tasks due to their minimalist hardware. Further projects and applications require upgrades and enhancements. A special role is played by the subrack Z 1013.50, which provides four expansion slots along with appropriate amplification and control electronics. One of these wells, however, permanently from the power supply module Z 1013.40 substantiated as recommended by the manufacturer for the Z 1013 power adapter is not designed to operate additional modules. All slots of the rack are plug compatible with the extensions of the computer Z 9001, KC 85/1 and KC 87, wherein the modules must often be modified slightly for use. If the rack with the Z 1013.64 be operated at both respective changes should be made. 
=== Memory and additional interfaces ===
In order to upgrade the RAM, the manufacturer recommends the use of a RAM module, the computer Z 9001, KC 85/1 and 87 KC with the type designation 1.40.690003.5. In addition, there is a free unpopulated ROM module of Robotron, which can accommodate up to five EPROMs of the same type previously described by the user, each with a storage capacity of 2 KB.
With two expansion modules, the address range in which they are to be displayed by previously has DIP switches are set. The retrofitting of additional input and output interfaces are provided with the module Z 1013.30 which three freely usable I/O ports and a V.24 provides interface for control, for example printers. 
In addition to the modules sold by Robotron, user solutions that were prepared in larger quantities, and often as a mass storage replacement (existing RAM disk ), were used. The most widely used version of Präcitronic with 256 KB RAM (64 KB RAM and 192 KB memory bank), in 1988 in the journal Microprocessor Electronics, was presented together with PCB manufacturers and adapted shortly thereafter for use with the Z1013. With appropriately modified system software, RAM disks were often used as replacement cassette recorder used.  
=== Keyboard and joystick port ===
The membrane keyboard of the Z-1013 computer had an 8 × 4 matrix of alphabetically arranged letters.
The membrane keyboard included in the kit needed to be connected by the user before first use via a ribbon cable to the computer circuit board. The keys were arranged alphabetically in matrix 4 × 8 and the contact in the membrane switch proved to be unsatisfactory, the keys tended to bounce . An effective work was almost impossible.  Soon, were part of many users desired alternatives and also developed. As a standard solution for connecting more comfortable keyboards with QWERTY arrangement of 1988 sat in the journal microprocessor technology to a broad public presented Brosig monitor with instructions for building a hardware interface through. Besides additional utilities and backward compatibility for system software from Robotron of 4KB comprehensive Brosig monitor also offers the ability to operate joysticks on the computers. 
With the help of an additional module available separately to the Z 1013.64 keyboards with 64 keys, as they were shipped with most DDR-office computers are operated. 
=== Graphics modules ===
The improvement of the graphical capabilities were devoted to various articles in magazines and brochures. These include instructions for building various extensions of varying scope and also the notes for acquisition by purchase of prefabricated modules. The spectrum ranges from improved character generator solutions (developed by the Computer Club Jena graphics card GDC 80 × 25 characters) monochrome high-resolution pixel graphics (256 x 256 solution KRT graphics in micro computer tips 11  and 256 × 192 Card Spectrum graphics in the Journal Practic  ) to proposals of multicolored high-resolution versions (384 × 288 Card VIS3 with 16 colors of the Academy of Sciences  ). Robotron itself offered no such upgrades. 
== Software ==
When existing software is mainly to in-house developments from the GDR. Machine-porting of programs western Z80-based home computer systems were very expensive due to technical differences in the rule. The easiest is the exchange program and the corresponding adaptation of software with the computers of the series Z 9001, KC 85/1 and KC 87
The proliferation of software and the exchange of experiences carried out mainly through private contacts as well as newspaper ads, trade shows, by insertion of programs in magazines and broadcast on the radio, such as in the broadcast Rem .  From the state was the creation software, for example, about the Society for Sport and Technology (GST) with their computer section Sports promoted. Often, the GST was also one of the organizers of meetings and conferences.
Restrictions on the disclosure by copyright protection or copy protection mechanisms did not exist in practice. Rather, the free distribution of software ("Amateur Software") was promoted and confirmed in relevant meetings.  For the Z 1013 more than 500 programs and hardware extensions have been developed and published. 
=== System Tools ===
To configure the computer hardware to drive the cassette interface and to enter and read-out of memory addresses that serves operating system contained in the ROM of the device monitor program 2:02 at Z 1013.01, Z 1013.12 and Z 1013.16 or monitor program A.2 at Z 1013.64. The system software of the Z 1013.64 enables a subsequent connection of a comfortable keyboard with 58 keys, in contrast to those of previous Z-1013 models, which include a maximum of 32 keys. 
Besides Robotrons monitor programs exist other system software from third parties that can be upgraded with the help of the user EPROM. This is particularly noteworthy in 1987 presented and subsequently widespread Brosig monitor, which is backward compatible with the system software of Robotron. In addition to useful utilities of 4KB comprehensive Brosig Monitor provides including the ability to operate the computer models Z and Z 1013.01 1013.16 with comfortable keyboards and joysticks.   
On computer models, which have a RAM disk, the operation is with the CP/M based system software SCP possible. Thus, some programs from the extensive library SCP are also available for the Z-1013 computer. 
=== Programming Languages and Applications ===
Due to the limited graphics and sound generating options, the Z-1013 machines were mainly used for programming and for applications such as word processing. There are also some games that get along with monochrome graphics and without background music, such as the chess programs Chess master and Cyrus-Chess.
For programming the Z 1013 different programming languages and tools are available. In addition assemblers ( 5.3 scf assembler, editor / assembler EDAS ) are high level languages such as Tiny-BASIC, KC-BASIC, BASICODE, Forth and Pascal available. 
== Literature ==
Special magazines for the Z 1013 and other home computers in general there was not. Magazines such as Funkamateur, Jugend und Technik, MP – Mikroprozessortechnik und Practic regularly published news, reports, craft instructions for building your own additional hardware or upgrading and conversion of computer programs as well as for typing.
The VEB Robotron Elektronik Riesa served as editor of the written by Hannes Gutzer and Gerd Hutterer brochure BASIC with the Z 1013, which had the programming using the BASIC interpreter of Z in 1013 on the topic.
Even after the German reunification the same interests in private publications and from the late 1990s, within the following of DDR-computing technology also maintained in Internet forums further, to the creation of appropriate emulators. 
== Emulation ==
After the end of Heimcomputerära the early 1990s and with the advent of powerful and affordable computing technology mid-1990s programs were strengthened by dedicated enthusiasts to emulate developed by home computers and their peripherals. To play old classics various home computer systems ranges with the help of emulators, a single modern system with data images ("Images") of the corresponding home computer programs. The advent of emulators sat thus, inter alia, an increased transfer of otherwise potentially lost software on modern storage media in transition, making an important contribution to the preservation of digital culture is made. 
To emulate the GDR small computer, especially the Z 1013, which runs under Windows and Linux emulation package was JKCEMU developed. 
== Reception ==
=== Contemporary ===
In contrast to the computers of the KC series, was the Z 1013 also for private users - but only after ordering, long waiting time and personal pickup in Erfurt or Riesa - available. The reason for the restricted distribution was the refusal of international trade to drive the Z-1013 kit, on the grounds that a craft unit will encounter in the population to little interest. 
From the state-controlled magazines such as Radio Television electronics and amateur radio the appearance of the computer, however, was greeted: "As close to the hardware, reasonably priced and well documented system" he was perfectly suited to the "experimental appropriation of skills in the field of applied micro-computer technology". [35 ]  At the same time, however, was that initially the Z 9001 and KC 85/1 incompatible BASIC, incompatibilities of the cassette interface for the differently clocked variants and especially useless for extensive text input foil flat keyboard as "the weak point of the Z 1013" criticized. [37 ]  Overall, the Z 1013 was classified as a viable device "for electronics amateurs, beginners and advanced, amateur radio, and social support needs of teaching and training." 
The popularity of the computers in the population manifested itself in a variety of organized computer clubs with frequently held local meetings to high traffic national meetings that were held annually and serve for example for exchanging software, experience and set of programming standards. 
=== Retrospective ===
More recently, are developed and produced in the GDR computer, including in particular small computer and video gaming machines, again reinforced above all perceived in the media, on the Internet and also exhibited in special museums. Here, the Z 1013 is characterized as ajar to Western single-board self-development, despite the fact that many electronic components such as the microprocessor U880 is a copy of the Western Z80 microprocessor from Zilog. In contrast to the GDR minicomputers from Dresden and Mühlhausen was the Z 1013 "with open design available in several versions as a consumer over the entire production period, but without being able to meet the demand." Which examines the historical elaboration of Robotron computer technology working group in the Technical Collections Dresden characterizes the distribution of the environment Z in 1013 as follows:
"This relatively inexpensive microcomputer kit therefore came in the home but also in computer clubs and associations and in a few cases in the industry for the use. He was well suited for immediate get to know the internal workings of micro-computer technology, for learning programming, to build their own computer for creative hobby applications, and numerous hardware and software improvements and enhancements. "
- Klaus-Dieter way : product line home computers, mini-computers and computer education of the VEB Kombinat Robotron. 
Even if the kit in the GDR was very popular, the technological backwardness of the computer compared to the products of Western industrialized countries always about three to five years was at the time of their appearance: was defined as the production of the Z 1013 recorded in East Germany, were in the West already affordable 16-bit computers like the Atari ST and Commodore Amiga available for private households.  
After the decline in demand, oversupply, despite considerable selling price reductions in 1989 and 1990. A continuation of the production of the MRB Z 1013 in 1990 in view of the expected range of other Western competitors no longer profitable, whereupon the production of the Z 1013 and mid-1990, set up the equipment in the warehouse remainder of scrapping was fed. 
== Literature ==
Klaus-Dieter Weise: Erzeugnislinie home computers, mini-computers and computer education of the VEB Kombinat Robotron. history of the Robotron UAGworking group computing technology in the Technischen Sammlungen Dresden, Dresden 2005, (PDF; 590 KB).
== References ==
Robotron Z1013 (English)
== External links ==
J1013 (Java Z1013 emulator)
Mikrorechnerbausatz MRB Z1013
Z1013 software-database comprehensive collection of binaries and documentation