Retrocomputing

1596 Articles

A Curiously Strong Z80 In Your Pocket

September 17, 2019 by 42 Comments

Like many hackers, [Tom Szolyga] has soft spot for the venerable Z80. The number of instructions and registers made it relatively easy to program in ASM, and he still has fond memories of the refreshingly straightforward CP/M operating system he used to run on them back in the day. In fact, he loves Z80 computers so much he decided to build one that he could carry around in his pocket.

The result is the Minty Z80, so-called because it lives inside a tin formerly inhabited by every hacker’s favorite curiously strong mint. But the goal of this build wasn’t just to make it small, but also make it convenient to work with. [Tom] is using a ATmega32A to help interface the Z84C0008 microprocessor with the modern world, which allows for niceties such as support for a micro SD card. There’s no onboard USB-to-serial capability, but with an external adapter connected to the Minty’s header, it’s easy to use log into this microcosm of classic computing with a terminal emulator running on a computer or mobile device.

[Tom] has provided the schematics and Bill of Materials for the Minty Z80 on the project’s Hackaday.io page, but as of the latest update, he’s holding off on releasing the board files until he’s sure that all the bugs have been worked out. There’s no word yet if he found any show stoppers in the first iteration of the board design, but he’s posted a picture of the fully assembled miniature retrocomputer in all its glory which seems like a good sign.

The design of the Minty Z80 is similar to that of the Z80-MBC2 by [Just4Fun], but on an even smaller scale. It’s encouraging to see several projects leveraging modern design and components to prevent classic computing from becoming little more than a distant memory.

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Upping The Story-Telling Game With Dialog And The Å-Machine

September 16, 2019 by 5 Comments

During the decades since Infocom released their interactive story game Zork to world-wide acclaim for microcomputers, the genre of interactive fiction (IF) is still immensely popular, with a surprising number of modern IF works targeting Infocom’s original Z-Machine runtime for 8-bit micocomputers. We’ve seen a number of improved runtimes and languages for the platform over the years, with [Linus Åkesson]’s Dialog language a newcomer.

Covering the technical details about the language in this thread at IntFiction, the interesting aspect about this language is that while it has a compiler that compiles it to Z-code for the Z-Machine, [Linus] has also implemented a new runtime, called the ‘Å-Machine‘, since ‘Å’ follows ‘Z’ in the alphabet (if you’re Swedish, that is). This runtime should allow for larger stories and other features that make better use of more resources, while still allowing smaller stories to work on old hardware. Unfortunately the only Å-Machine implementation at this point is written in JavaScript, which is not known to work particularly well on Commodore 64 or even Amiga 500 systems.

As for Dialog itself, its documentation provides a detailed overview of the language’s capabilities, which claims to be inspired by both Inform 7 and Prolog. Its goals are to be easy to follow, with a minimal number of language concepts, and high performance. As the documentation notes, many Z-Machine based stories exist today that are unplayable on vintage hardware due to lack of optimization.

We covered Zork and the Z-Machine a while ago in some detail. We think it’s great to see that there’s still so much interest in the platform. Maybe someone will write an Å-Machine implementation for a Commodore or MSX system one of these days to see how it compares to Infocom’s Z-Machine. Here’s to another few decades of the Zork-legacy.

Teaching A Vintage Line Printer To Make Music, All Over Again

September 13, 2019 by 8 Comments

Sit next to any piece of machinery long enough and you get to know it by the sounds it makes. Think about the sounds coming from any 3D-printer or CNC machine; it’s easy to know without looking when the G code is working through the sines and cosines needed to trace out a circle, for instance.

It was the same back in the day, when bored and bright software engineers heard note-like sounds coming from their gear and wrote programs to turn them into crude music machines. And now, [Ken Shirriff] details his efforts to revive a vintage IBM 1403 line printer’s musical abilities. The massive 1960s-era beast is an irreplaceable museum piece now, but when [Ken] and his friends at the Computer History Museum unearthed stacks of punch cards labeled with song titles like “Blowin’ In the Wind” and “The Blue Danube Waltz,” they decided to give it a go.

The 1403 line printer has a unique chain-drive print head, the inner workings of which [Ken] details aptly in his post. Notes are played by figuring out which character sequences are needed to get a particular frequency given the fixed and precisely controlled speed of the rotating chain. The technique is quite similar to that used by musical instruments such as the Floppotron, or when coercing music from everyday items including electric toothbrushes.

Lacking the source code for the music program, [Ken] had to reverse engineer the compiled program to understand how it works and to see if playing music would damage the chain drive. The video below shows the printer safely going through a little [Debussy]; audio clips of songs originally recorded back in 1970 are available too.

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How Many Commodores Does It Take To Crack A Nut?

September 7, 2019 by 19 Comments

It’s brilliant enough when composers make use of the “2SID” technique to double the channels in a Commodore 64 with two sound chips, but even then some people like to kick things up a notch. Say, five times more. [David Youd], [David Knapp] and [Joeri van Haren] worked together to bring us just that, ten Commodore computers synchronously playing a beautiful rendition of the Dance of the Sugar Plum Fairy at this year’s Commodore Retro eXpo.

The feat is composed of nine Commodore 64 computers and one Commodore 128, all fitted with the SID chip. It is a notorious synthesizer chip for utilizing both analog and digital circuitry, making each and every one of its revisions unique to a trained ear, not to mention impossible to faithfully reproduce in emulation. The SID was designed by Bob Yannes at MOS Technology, who later went on to co-found Ensoniq with his experience in making digital synthesizers.

How this orchestra of retro computers came to be, including details on how everything is pieced together can be found on this slideshow prepared by the authors of the exhibition. It’s interesting to note that because of timing differences in each computer’s crystal clock and how only the start of the song is synchronized between them, they can’t play long music tracks accurately yet, but a 90-second piece works just fine for this demonstration.

These synthesizer chips are slowly going extinct since they’re no longer being manufactured, so if you need a new replacement solution, FPGAs can fill that SID-shaped hole in your heart. If you need the whole computer though, the newer Teensy 3.6 will do just fine emulating it all. Check out this beast of a display in action after the break. While we’re at it, this isn’t the only time multiple 8-bit computers have been combined as an orchestra, though these Commodores sound a lot better than a table full of ZX Spectrums.

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DIY 40FPS 16bpp Platformer On A Cortex M0+

September 2, 2019 by 8 Comments

Sure, you can play a bunch of retro games on a Raspberry Pi, but if you’re really hardcore, you build your own retro console and write your own games for it. [Nicola Wrachien]’s entry into this year’s Hackaday prize is his DIY Cortex M0+ game console and the platform game he wrote to test the hardware.

The board that [Nicola] is using is the uChip, a small DIP board based around a ATSAMD21 (the same chip that runs the Arduino Zero). That, along with a 160×128 TFT LCD screen, makes up the bulk of the hardware. A carrier board holds both of these as well as several buttons and an OpAmp.

The ATSAMD21 chip has decent hardware DMA that [Nicola] is using to get the frame rate needed. Since the DMA hardware and the CPU can work at the same time, while the DMA is handling one chunk of graphics, the CPU is working on the next chunk. Using this system, [Nicola] is able to get a better framerate than originally designed. Take a look at [Nicola]’s webpage for more details on the algorithm used.

In order to create a level in the platformer that [Nicola] made to show off the console, [Nicola] created a full blown level editor in Java. Using the editor, you can place the tiles and sprites and set their behaviours. The map can then be exported in an optimized format for loading on to the hardware and into the game.

A video showing off the game is after the break. There’s no shortage of great DIY consoles on the site — check out this impressive vector console, or if RetroPie is more your thing, take a look at this DIY Zelda-playing device.

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Another World On The Apple II

August 26, 2019 by 11 Comments

What’s more fun than porting an old game released for an old system such as the Apple IIgs to its 10-year-older predecessor, the Apple II from 1977? Cue [Deater]’s port of the classic video game ‘Another World‘ to the original Apple II. As was fairly obvious from the onset, the main challenges were with the amount of RAM, as well as with the offered graphics resolutions.

Whereas the Apple II could address up to 48 kB of RAM, the 16-bit Apple IIgs with 65C816 processor could be upgraded to a maximum of 8 MB. The graphics modes offered by the latter also allowed ‘Another World’ to run at a highly playable 320×200, whereas the ported version is currently limited to the ‘low resolution’ mode at 40×48 pixels.

The game itself still needs a lot of work to add missing parts and fix bugs, but considering that it has been implemented in 6502 assembler from scratch, using just the gameplay of the IIgs version as reference, it’s most definitely an achievement which would have earned [Deater] a lot of respect back in the late ’80s as well.

Feel free to check out the Github page for this project, grab a floppy disk image from the project page and get playing. Don’t forget to check out the gameplay video linked after the break as well.

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Vintage Console Becomes The Calculator It Appears To Be

August 25, 2019 by 9 Comments

What’s sitting on [Bob Alexander]’s desk in the video below did not start out life as the desktop calculator it appears to be. Turning it into a standalone calculator with features the original designers couldn’t imagine turned out to be an interesting project, and a trip down the retrocomputing rabbit hole.

A little explanation is in order. Sure, with its Nixie display, calculator keypad, and chunky mid-century design, the Wang 360 desktop console looks like a retro calculator. But it’s actually only a dumb terminal for a much, MUCH bigger box, called the Electronic Package, that would fit under a desk. The foot-warming part that was once connected to [Bob]’s console by a thick cable that had been unceremoniously lopped off by a previous owner. [Bob] decided to remedy the situation with modern electronics. The console turned out to have enough room for a custom PCB carrying a PIC32, some level-shifting components, power supply modules that include the high-voltage supply for the Nixies, and a GPS module because Nixies and clocks just go together. The interesting bit is the programming; [Bob] chose to emulate the original Wang methods of doing math, which include multiplication by logarithmic addition. Doing so replicates the original look and feel of the calculator down to the rapid progression of numbers across the Nixies as the logarithms are calculated using the display registers.

We normally frown on vintage gear being given modern guts, but in this case [Bob] hit just the right balance of new and old, And given that the Electronic Packages these consoles were connected to go for $1500 or more on eBay, it was a better choice than letting the console go to scrap. A similarly respectful approach was taken with this TRS80 Model 100 revival.

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