Galaksija (computer)

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Galaksija
Galaksija 1984.jpg
Main board of Galaksija during assembly process
Type Home computer
Release date1983
Media Cassette tapes
CPU Zilog Z80A clocked at 3.072MHz
Memory2-6KB RAM, 4-8KB ROM
Display64x48 monochrome
Input Keyboard
Successor Galaksija Plus

The Galaksija (pronounced GalaxiyaSerbo-Croatian:  [galǎksija] , meaning Galaxy) was a build-it-yourself computer designed by Voja Antonić. It was featured in the special edition Računari u vašoj kući [1] (Computers in your home, written by Dejan Ristanović) of a popular eponymous science magazine, published late December 1983 in Belgrade, Yugoslavia. Kits were available but not required as it could be built entirely out of standard off-the-shelf parts. It was later also available in complete form.

Voja Antonić Serbian inventor, journalist and writer

Vojislav "Voja" Antonić is a Serbian inventor, journalist and writer. He was also a magazine editor and contributed to a number of radio shows but he is best known for creating a build-it-yourself home computer Galaksija and originating a related "Build your own computer Galaksija" initiative with Dejan Ristanović. This initiative encouraged and enlightened thousands of computer enthusiasts during the 1980s in the Socialist Federal Republic of Yugoslavia. Mr. Antonić donated many of his personally creations to the public domain, whenever they related to the common people or a fellow engineer.

Dejan Ristanović Serbian writer

Dejan Ristanović, is a well known Serbian writer and computer publicist.

Contents

History

In the early eighties, various laws in Yugoslavia prevented importing computers into the country. At the same time, even the cheapest computers available in the West were nearing average monthly salaries. This meant that regardless of demand for home computers, only a relative minority of people owned one – mostly a ZX Spectrum or a Commodore 64.

Socialist Federal Republic of Yugoslavia socialist republic in Southeast Europe between 1943 and 1992

The Socialist Federal Republic of Yugoslavia was a country located in central and Southeastern Europe that existed from its foundation in the aftermath of World War II until its dissolution in 1992 amid the Yugoslav Wars. Covering an area of 255,804 km², the SFRY was bordered by the Adriatic Sea and Italy to the west, Austria and Hungary to the north, Bulgaria and Romania to the east, and Albania and Greece to the south.

ZX Spectrum series of personal home computers

The ZX Spectrum is an 8-bit personal home computer released in the United Kingdom in 1982 by Sinclair Research.

Commodore 64 8-bit home computer introduced in January 1982

The Commodore 64, also known as the C64 or the CBM 64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 10 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the Commodore VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes(65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.

According to his own words, [2] some time in 1983, Voja Antonić, while vacationing in Hotel Teuta in Risan, was reading the application handbook for the RCA CDP1802 CPU and stumbled upon CPU-assisted video generation. [2] Since the CDP1802 was very primitive, he decided that a Zilog Z80 processor could perform the task as well.

Risan Town in Kotor Municipality, Montenegro

Risan is a town in the Bay of Kotor, Montenegro. It traces its origins to the ancient settlement of Rhizon, the oldest settlement in the Bay of Kotor.

RCA 1802

The RCA CDP1802, a 40-pin LSI integrated circuit chip (IC), implemented using COSMAC architecture, is an 8-bit CMOS microprocessor (µP) introduced by RCA in early 1976, the company's first single-chip microprocessor. Within RCA in the early days, the 1801 and 1802 microprocessors were sometimes referred to as "the COSMAC". Hobbyists usually refer to it simply as "the 1802". It is currently being manufactured by Intersil Corporation as a high-reliability microprocessor. The 1802 has an architecture different from most other 8-bit microprocessors.

Central processing unit electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions

A central processing unit (CPU), also called a central processor or main processor, is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions. The computer industry has used the term "central processing unit" at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.

Before he returned home to Belgrade, he already had the conceptual diagrams of a computer that used software to generate a video picture. Although using software as opposed to hardware would significantly reduce his design's performance, it also simplified the hardware and reduced its cost.

Belgrade City in Serbia

Belgrade is the capital and largest city of Serbia. It is located at the confluence of the Sava and Danube rivers and the crossroads of the Pannonian Plain and the Balkans. The urban area of the City of Belgrade has a population of 1.23 million, while nearly 1.7 million people live within its administrative limits.

His next step was to find a magazine to publish the diagrams in. The obvious choice was SAM Magazine published in Zagreb, but due to prior bad experiences he decided to publish elsewhere. [2]

Zagreb Capital and largest city of Croatia

Zagreb is the capital and the largest city of Croatia. It is located in the northwest of the country, along the Sava river, at the southern slopes of the Medvednica mountain. Zagreb lies at an elevation of approximately 122 m (400 ft) above sea level. The estimated population of the city in 2018 is 810,003. The population of the Zagreb urban agglomeration is about 1.2 million, approximately a quarter of the total population of Croatia.

The popular science magazine Galaksija appeared incompatible but he heard that they were working on a special issue dedicated to computers. He proposed publishing entire do-it-yourself diagrams, instructions, etc. to the author of the issue, Dejan Ristanović. Everything made its way into the special issue called Računari u vašoj kući (Computers in your home). It was released late December 1983, although it was dated January 1984.

They tried to guess the number of Galaksijas that would be built by readers. Their estimates ranged from a hundred to a thousand (a number that sounded so optimistic it provoked laughter). The actual number built by known "do-it-yourselfers" – was around 8000! [2] This number may in reality be greater if people who did not purchase any kits (including PCB and ROMs) are accounted for.

Components were provided by various manufacturers and suppliers:

Later, Institute for school books and teaching aids together with Elektronika Inženjering started mass commercial production of Galaksija computers, mainly to be delivered to schools.

Technical specifications

BASIC ROMs

Galaksija BASIC is a BASIC interpreter originally partly based on code taken from TRS-80 Level 1 BASIC, which the creator believed to have been a Microsoft BASIC. [2] However, after extensive modifications to include video generation code (as the CPU was a major participant to reduce the cost of hardware) and improve the programming language, what remained from the original is said to be mainly flow-control and floating point code. It was fully contained in 4 KB ROM "A" or "1". Additional ROM "B" or "2" provided more Galaksija BASIC commands, assembler, monitor, etc.

ROM "A"

The chip labeled as "A" by the creator of Galaksija, Voja Antonić was commonly referred to as "ROM 1" or just "ROM". ROM "A" contained bootstrap code of Galaksija, its control code (rudimentary operating system), video generation code (as Galaksija did not have advanced video subsystem its Z80 CPU was responsible even for generating video signal) and Galaksija BASIC.

Fitting all this functionality in 4 KB of 2732 EPROM required a lot of effort and some sacrifices. For example, some message text areas were also used actual code (e.g. "READY" message) and the number of error messages was reduced to only three ("WHAT?", "HOW?" and "SORRY").

ROM "B"

ROM "B" of the Galaksija is a 2732 EPROM chip that contains extensions to the original Galaksija BASIC available in base ROM ("A"). It was labeled as "B" by the creator of the Galaksija, Voja Antonić, but was commonly referred to as "ROM 2".

ROM "B" contained added Galaksija BASIC commands and functions (mostly trigonometric) as well as a Z80 assembler and a machine code monitor. This ROM was not required and was an optional upgrade. Although planned on the mainboard, the content of ROM "B" was not automatically initialized during booting. Instead, users had to execute a Galaksija BASIC command to run a machine code program from ROM "B" before they can gain additional features. This also meant that even Galaksijas with ROM "B" plugged in can behave entirely as base models.

Character ROM

Character ROM of home computer Galaksija is a 2716 EPROM chip that contains graphical definitions of Galaksija's character set. It had no special name and was labeled "2716" after the type of 2 KB EPROM needed.

Galaksija had a slightly modified (localized) ASCII character set:

Each character was represented as 8x13 matrix of pixels. In this ROM, 8-pixel rows of each character are represented as 8 bits of one byte.

"Cassette" port

Galaksija used cassette tape as secondary storage. It featured a 5-pin DIN connector used to connect the computer to a cassette tape recorder. Tape interface circuitry was rudimentary – other than few elements controlling the levels it was essentially one-bit digital equivalent to the one in the ZX Spectrum. The input signal was routed to the integrated circuit otherwise responsible for keyboard, so the CPU would "see" the input signal as a series of very fast key presses of varying lengths and gaps between them.

It is normally stated that original Galaksija does not have any dedicated (separate) audio ports and most of the programs were written as silent. It was, however, possible to utilize the cassette tape port as an audio output as well like it is done in ZX Spectrum (its "EAR" connector). The only technical difference between ZX Spectrum and Galaksija in regards to existence of audio is that ZX Spectrum has a built-in beeper, while Galaksija's plans do not include any kind of a speaker.

Design

To simplify "do-it-yourself" building and reduce cost, the printed circuit board was designed as single-layer (one-side) board. This resulted in a relatively complicated design requiring many components-side connections to be made using wires.

Galaksija's case was not pre-built. Instead, the guide suggested it to be built out of the printed circuit board material (such as Pertinax) also used for the mainboard. Thus, the top, sides and reinforcements were soldered together to form the "lid". acrylic glass was recommended for the underside. The guide included instructions on cleaning, painting and even decorating the assembled case. The name "GALAKSIJA" and decorative border were to be added using Letraset transfer letter sheets after the first (white) coat of paint but before the second coat of final colour. After the paint dried, transferred decorations were supposed to be scratched off, exposing underlying white paint.

The keyboard is laid out such that keys have their own memory-mapped addresses that, in most cases, follow the same order as ASCII code of the letter on the key. This saved the ROM space by reducing lookup tables but significantly increased the complexity of single-layer keyboard PCB such that it alone required 35 jumpers.

See also

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References

  1. Računari u vašoj kući
  2. 1 2 3 4 5 Antonić, Voja. "1983: Galaksija". Archived from the original on 4 May 2009. Retrieved 17 June 2010.

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