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The Galaksija was a build - it - yourself computer designed by Voya Antonich. It was featured in the special edition Computers in your home (Racunari u vasoj kuci) of a popular eponymous science Galaksija 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.

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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. Everything made its way into the special issue called Racunari u vasoj kuci (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 ROMs) are accounted for.

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TECHNICAL SPECIFICATIONS

  • CPU: Zilog Z80A 3.072 MHz;
  • ROM "A" or "1" 4 KB (2732 EPROM) contains bootstrap, core control and Galaksija BASIC 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 static RAM in base model, expandable to 54 KB;
  • Text mode 32 X 16 characters, monochrome;
  • Pseudographics: 2 X 3 dot matrix combinations in graphic character subset 64 X 48 dots total;
  • Sound: None according to specifications, but tape interface was occasionally used as audio output port;
  • Storage media: cassette tape, recording at 280 bit / s rate;
  • I / O ports: 44 - pin edge connector with Z80 Bus, tape (DIN connector), monochrome video out (PAL timings, DIN connector), and UHF TV out (RCA connector).

 

  • : Zilog Z80A 3,072 ;
  • : 64 , 8 , ;
  • A: 4   , , Galaksija BASIC;
  • B (): 4   Galaksija BASIC, , ;
  • : 2 ;
  • : 2...6 , 54 ;
  • : , 32 X 16 , ;
  • : 2 X 3 , 64 48 ;
  • : 54 ;
  • : , ;
  • : , 280 ;
  • : 44 ;
  •  - DIN - ;
  • PAL - DIN - ;
  •  - RCA - .

Scheme of PC "Galaksija" is presented in figure (scheme cliccabile). The following is a list of parts used.

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VIDEO GENERATION

Galaksija did not have a dedicated video circuitry. Its Z80A CPU was directly responsible for modulating the monochrome video signal with a little help of a shift register. Galaksija's CPU would write one byte to the shift register, which would, in turn, serialize its 8 bits one by one to the video output.

Since Galaksija had little RAM, a portion of it was taken not to store information for each pixel separately but character codes. CPU then had to look up character definitions in its character definitions ROM to find the values to send to the shift register.

This was the standard operation available in Galaksija's ROM. Some software, however, reportedly took the responsibility for driving the shift register (and thus generating video) and was able to use various tricks to achieve what appears as high - resolution graphics, such as with user defined graphic characters.

Approximately 70 % of CPU time was used just to generate video, which made Galaksija relatively slow in normal operation. This was unacceptable while saving or loading data from the tape so video generation was disabled during tape operations. There is also a way to disable (and re - enable) video generation from BASIC when "fast computation" is required. With video disabled, the built-in BASIC interpreter was in many instances able to outperform interpreters of other home computers of the time.

"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. 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. Galaksija's plans do not include any kind of a speaker.

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PCB diagram of PC "Galaksija" is presented in figures below (figures cliccabile).

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List
File /
Scheme of PC "Galaksija"
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Scheme of power supply
Scheme of PC "Galaksija" from Fifan
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Binary file for EPROM 2732 (A)
2732 (A)
Binary file for EPROM 2732 (B)
2732 (B)
Binary file for EPROM 2716 (F)
2716 (F)
Gerber files for the production of PCB
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