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   » » Wiki: Galaksija (computer)
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The Galaksija (pronounced Galaxiya , meaning Galaxy) was a build-it-yourself computer designed by Voja Antonić. It was featured in the special edition Računari u vašoj kući Računari u vašoj kući ( Computers in your home, written by Dejan Ristanović) of a popular eponymous science magazine, published late December 1983 in , . 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.


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 or a Commodore 64.

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

Before he returned home to , 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.

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

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! This number may in reality be greater if people who did not purchase any kits (including PCB and ) are accounted for.

Components were provided by various manufacturers and suppliers:

  • and from , together with Institut za elektroniku i vakuumsku tehniku ( Institute for electronics and vacuum technology) delivered PCBs, keyboards and masks,
  • from sent integrated circuits
  • Voja Antonić personally programmed all
  • Galaksija collected requisition forms and organized deliveries

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
  • CPU: Z80A 3.072
  • ROM "A" or "1" – 4 KB (2732 ) contains bootstrap, core control and interpreter code
  • ROM "B" or "2" – 4 KB ( optional, also 2732 EPROM) – additional Galaksija BASIC commands, assembler, machine code monitor, etc.
  • Character ROM – 2 KB (2716 EPROM) contains character definitions, characters are 8 x 13 pixels, the block graphics were vertically divided in a 4:5:4 scheme, and horizontally in a 4:4 scheme.
  • RAM: 2 to 6 KB of 6116 in base model, expandable to 54
  • 32 x 16 characters,
  • : 2x3 combinations in graphic character subset – 64x48 dots total. More was done using tricks – see video generation.
  • Sound: None according to specifications, but tape interface was occasionally used as audio output port – like the "EAR" port on can be used both as audio and cassette port. See cassette port for details.
  • : , recording at 280 rate
  • I/O ports: 44-pin with Z80 Bus, tape (), monochrome video out ( timings, ), and UHF TV out ()


BASIC ROMs
is a interpreter originally partly based on code taken from TRS-80 Level 1 BASIC, which the creator believed to have been a . However, after extensive modifications to include video generation code (as the 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 and code. It was fully contained in 4 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 code of Galaksija, its control code (rudimentary ), video generation code (as Galaksija did not have advanced video subsystem its Z80 was responsible even for generating ) and .

Fitting all this functionality in 4 KB of 2732 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"
"B" of the Galaksija is a 2732 chip that contains extensions to the original 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 ) 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 . Instead, users had to execute a Galaksija BASIC command to run a 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 of Galaksija is a 2716 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) character set:

  • There were no lowercase characters
  • Codes 91 to 94 represented characters Č, Ć, Ž and Š, respectively. Letter "Đ" was not present in original version and was commonly replaced with "DJ".
  • It contained 64 pseudo-graphics characters, having different combinations of dots in 2x3 .
  • Character codes 64 and 39 are used for two-halves of the logo of Elektronika Inženjering company (they can be seen in "READY" prompt)

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


"Cassette" port
Galaksija used as secondary storage. It featured a 5-pin 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 . 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 (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 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 . Thus, the top, sides and reinforcements were together to form the "lid". 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 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 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.

== Gallery ==


See also
  • – details about Galaksija's programming language
  • – improved version of Galaksija, announced in Jun/July 1984 (6th) issue of "Računari" magazine (: Computers, renamed from "Računari u vašoj kući")
  • Voja Antonić – the creator of Galaksija
  • Dejan Ristanović – well known writer and computer publicist who authored much of the special issue magazine featuring Galaksija
  • Z80 – Galaksija's
  • ZX80 - Sinclair ZX80 which predates the Galaksija by 4 years and has a remarkably similar system design including using the Z80A to drive the video output.


External links

Articles
  • Computers in your home – short overview by Dejan Ristanović, the author of Računari u vašoj kući magazine issue, in English language
  • 1983: Galaksija – how it all started, by Galaksija's creator Voja Antonić himself (in )
  • Computer Galaksija – detailed description of computer operation for those planning to build it, as published in the Računari u vašoj kući magazine issue. Written by creator Voja Antonić, in Serbian language.
  • Uputstvo za upotrebu – complete, original, user manual on-line, in Serbian language.
  • Magazine Scans – scans of original magazine pages containing schematic diagrams, building and other instructions and programs for Galaksija (text in Serbian language)
  • Računar Galaksija by Dejan Ristanović, the author of Računari u vašoj kući magazine issue, in Serbian language


Presentations


Remake


Emulators


Online museums


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