The Soviet-Era, Z80-based Galaksija Dared to Be Different

Eastern European Cold War–period computing has a poor fame. The image is one in all a panorama plagued by uninspired makes an attempt to repeat American IBM PCs, British ZX Spectrums, and different Western computer systems. But then there was Yugoslavia’s Galaksija, a really impressed bid to place a pc into the arms of normal comrades.

The
Galaksija is a Z80-based, 8-bit DIY machine, cleverly designed in order that its invoice of supplies meshed precisely with what a Yugoslavian was in a position to import from Western Europe. During its temporary heyday, 1000’s had been constructed, resulting in commercially assembled Galaksijas discovering their means into houses and colleges throughout the nation. And now you possibly can do this scrappy machine for your self.

As a retrocomputing nerd, after I noticed early final yr that the Galaksija was being reissued as an entire equipment by means of
Crowd Supply, I positioned an order on basic ideas. But my curiosity was actually piqued a couple of months later after I attended a captivating speak on Yugoslavian computing given by Vlado Vince on the HOPE hacker convention. As delays stored pushing the supply of the Crowd Supply equipment again into an indefinite future, I bumped into Vince on the Vintage Computer Festival East final April, and he slipped me a spare Galaksija printed circuit board and a hyperlink to his trendy invoice of supplies. Figuring it was plain crusing from there, I canceled my Crowd Supply equipment order and set off alone.

Complete plans for the Galaksija had been first revealed in 1983 in an article within the laptop journal
Računari u vašoj kući as a three way partnership between the Galaksija’s designer, Voja Antonić, and the journal’s editor, Dejan Ristanović. (An English translation of the article was revealed by No Starch Press in 2018 inPoC||GTFO Vol. 2.) Yugoslavians who didn’t need to attempt ordering parts from abroad might organize them from Antoić and Ristanović.

The Galaksija initially used a single-sided PCB, however a couple of years in the past Antoić launched a two-layer revision. This primarily eliminates the necessity to solder in jumper wires, rushing up development significantly. The new model makes two different tweaks, with a brand new set of footprints for video and audio jacks, and an additional capacitor to repair a timing concern when utilizing the trendy variant of the Z80 CPU chip.

But even with these decadent concessions, you’ll nonetheless be getting a construct expertise that received’t really feel like something you’ve ever made for those who’re underneath 50. For starters, most of the resistor values used will appear just a little off. Modern designs sometimes revolve across the
E6 collection of ohmic worth multipliers—1.0, 1.5, 2.2, 3.3, 4.7, and 6.8. But you’ll want an E24 set readily available, as lots of Galaksija’s resistors have multipliers like 1.8 or 6.2.

The Galaksija makes use of comparatively few parts, counting on its CPU to do loads of the work that’s completed by devoted circuitry in different residence computer systems. Two EPROMs (recognizable by the window that enables their silicon to be uncovered to ultraviolet gentle for information erasure) retailer the working system, whereas a 3rd EPROM shops graphical character information.James Provost

Next, like some
different early residence computer systems, the Galaksijia has minimal video circuitry, relying largely on the CPU to generate analog tv indicators. This helped vastly in conserving its element prices throughout the authorized import restrict, though the extra computing overhead did gradual the Galaksija down considerably. The Galaksijia generates a European PAL TV sign, which I used to be in a position to make use of with a flat-screen monitor, due to the magic of my RetroTink-2X Pro, a beautiful little field that may convert many out of date video indicators to HDMI. You also can attempt plugging it into an previous analog American CRT TV, as a result of its pure black-and-white sign is compatible-ish with the NTSC customary, however I discovered this requires a forgiving TV and a very dab hand on the vertical maintain management.

But the massive complications are the Galaksija’s ROMs, with three chips in two flavors. These chips are
erasable programmable ROMs, or EPROMs, which will be electronically written to, as with trendy EEPROM chips. But to erase an EPROM it’s worthwhile to blast it with ultraviolet gentle for a couple of minutes by means of just a little round skylight window on high of its package deal.

Faced with a looming deadline, I did the one logical factor: I cheated.

I hadn’t dealt with an EPROM for the reason that Eighties, and that was a damaged one I used to be given to have a look at underneath my junior scientist microscope. I used to be in a position to supply some on eBay, however quickly realized that getting the chips was solely step one in all a sophisticated course of. Like many manufacturers, I take advantage of an inexpensive and cheerful
TL866-based ROM programmer. Out of the field, these can’t provide the upper voltage wanted to program an EPROM, though there are directions on-line for a {hardware} modification to permit this. But I used to be struggling to even learn the chips to confirm that they had been clean. Was there an issue with my device chain, or with the chips themselves? If my Galaksija did not activate correctly, how would I do know if the issue lay with the EPROMs or how I’d populated the board?

As seen on this diagram, tailored from EPROM inventor Dov Frohman’s 1971 paper for the IEEE Journal of Solid-State Circuits, every little bit of reminiscence is a transistor with an unconnected gate electrode [dark rectangle]. To set a bit, the gate is charged by making use of a excessive breakdown voltage between the transistor’s supply and drain, trapping electrons. The subject produced by the trapped gate electrons creates a conductive layer within the silicon substrate. The gate is reset by exposing the floor to penetrating UV gentle.James Provost

Faced with what seemed like a prolonged sequence of trial and error, and a looming deadline for this text, I did the one logical factor: I cheated. I emailed Vince, who conveniently additionally lives in New York City, and he volunteered to return into the
IEEE Spectrum workplace, alongside together with his UV EPROM eraser, hacked TL866 programmer, and a few programmed ROMs for testing. After about two hours of troubleshooting, together with tossing a dud chip, my Galaksija was displaying its READY immediate. Really, everybody ought to have an 8-bit Yugoslavian DIY laptop man: You might not want them for years, however whenever you do, you’re actually glad you’ve gotten them

You don’t must know Serbian or Croatian to program the Galaksija. It has a model of Basic utilized by the
TRS-80 Model 1, and therefore English key phrases. Software is saved and loaded by means of an audio jack initially supposed to interface with tape recorders, and there are collections of Galaksija software program accessible for obtain, together with classics like Tetris. The Galaksija is probably not as well-known as Western 8-bit machines just like the ZX Spectrum or Commodore 64, however attending to know it’s a good way to see how individuals elsewhere joined the digital revolution and the way motivated engineering can transcend main obstacles.