retrocomputing

334 Articles

The Bendix G-15 Runs 75,000 Lines Of Code

December 21, 2024 by 16 Comments

There’s a Blue Bendix in Texas, and thanks to [Usagi Electric] it’s the oldest operating computer in North America.  The Bendix G-15, a vacuum tube computer originally released in 1956, is now booting, and running code from paper tape. [David, aka Usagi] received the G-15 about a year ago from The System Source museum. The goal was to get the computer running so museum patrons could interact with a real tube computer. We’ve been following along since the project began.

[Usagi’s] latest G-15 video covers the last few problems on the road to running code. The biggest hurdle was the fact that the system wasn’t responding properly to the GO button on the typewriter. [Usagi] was able to isolate the issue down to a flip flop and then to a particular signal on an AND gate — the RC signal. The gate appeared to be bad, but swapping the entire circuit card multiple times had no effect. Something else had to be going on.

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Apple Newton Gets Rebuilt Battery Pack

December 13, 2024 by 14 Comments

We all carry touch screen computers around in our pockets these days, but before the smartphone revolution, there was the personal digital assistant (PDA). While it wasn’t a commercial success, one of the first devices in this category was the Apple Newton. Today they’re sought after by collectors, although most of the ones surviving to this day need a bit of rework to the battery pack. Luckily, as [Robert’s Retro] shows, it’s possible to rebuild the pack with modern cells.

By modern standards, the most surprising thing about these battery packs is both that they’re removable and that they’re a standard size, matching that of AA batteries. The Newton battery pack uses four cells, so replacing them with modern rechargeable AA batteries should be pretty straightforward, provided they can be accessed. This isn’t as easy, though. In true Apple fashion the case is glued shut, and prying it apart can damage it badly enough so it won’t fit back in the tablet after repair is complete. The current solution is to cut a hatch into the top instead and then slowly work on replacing the cells while being careful to preserve the electronics inside.

[Robert’s Retro] also demonstrates how to spot weld these new AA batteries together to prepare them for their new home in the Newton case. With the two rows fastened together with nickel strips they can be quickly attached to the existing electrical leads in the battery pack, and from there it’s just a matter of snapping the batteries into the case and sliding it back into the tablet. If you’re looking for something a bit more modern, though, we’d recommend this Apple tablet-laptop combo, but it’s not particularly easy on the wallet.

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Retro Computer Goes Back To The 1950s

December 6, 2024 by 24 Comments

When thinking of retrocomputing, many of us will imagine machines such as the Commodore 64 or Apple II. These computers were very popular and have plenty of parts and documentation available. Fewer will go back to the Intel 8008 or even 4004 era which were the first integrated circuit chips commercially available. But before even those transistor-based computers is a retrocomputing era rarely touched on: the era of programmable vacuum tube machines. [Mike] has gone back to the 1950s with this computer which uses vacuum tubes instead of transistors.

The computer has an eight-bit architecture and features most of the components of any modern transistor-based computer of similar computational ability. Memory, I/O, an arithmetic logic unit including a carry bit that allows it to do 16-bit arithmetic, are all implemented using 6N3P dual triode tubes that date to the 50s and 60s and would have been used in similar computers like the IBM 700. All of this drives a flight simulator program or a Fibonacci number generator, demonstrating its general purpose computing capabilities.

Of course, tubes were generally phased out in favor of transistors largely due to their power and space requirements; [Mike] needs a stepladder to maintain this computer as well as around ten minutes each time he starts it up to allow the tubes to warm up, with each module needing over three amps of current each. It’s a hugely impressive build and we’d recommend checking out the video linked below to get more details on its operation. If you’re looking for something a little more accessible to get into the world of vacuum tubes, this single-board tube computer fits the bill.

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KiCad render of µLind pcb

The 6809 8-Bit Microcomputer: A Father-Son Odyssey

December 6, 2024 by 22 Comments

If you’re nostalgic for the golden age of microprocessors and dream of building your own computer, this story might spark your imagination. [Eric Lind], passionate retro enthusiast and his 14-year-old son, embarked on a mission to craft a microcomputer from scratch, centred around the exotic Motorola 6809 chip: the µLind.

What sets this project apart is its ambition: bridging retro computing with modern enhancements. Starting with just a 6809 and some basic peripherals, the men designed a multi-stage roadmap to realize their dream. Each stage brought new challenges: debugging an address decoder, reworking memory management, and evolving glue logic into programmable GAL chips. Fascinatingly, the project isn’t just about nostalgia—it’s a playground for exploring multitasking operating systems and pushing the boundaries of 8-bit computing.

Their creativity shines in solutions like a C64-compatible joystick port, add-on expansion cards, and a memory overkill of 1MB RAM. With every setback—a missing pull-up resistor or a misrouted IRQ signal—their determination grew stronger. By combining old-school know-how with modern tools like KiCad, they’ve created something that is both personal and profoundly inspiring.

[Eric]’s hope and goal is to establish a community of people that want to expand beyond the traditional Z80 and 6502 based SBC’s. Interested? Read [Eric]’s project log on Hackaday.io and start crafting!

8-Bit Computers Crunch Advanced Scientific Computations

December 1, 2024 by 37 Comments

Although largely relegated to retrocomputing enthusiasts and embedded systems or microcontrollers now, there was a time when there were no other computers available other than those with 8-bit processors. The late 70s and early 80s would have seen computers with processors like the Motorola 6800 or Intel 8080 as the top-of-the-line equipment and, while underpowered by modern standards, these machines can do quite a bit of useful work even today. Mathematician [Jean Michel Sellier] wanted to demonstrate this so he set up a Commodore 64 to study some concepts like simulating a quantum computer.

The computer programs he’s written to do this work are in BASIC, a common high-level language of the era designed for ease of use. To simulate the quantum computer he sets up a matrix-vector multiplication but simplifies it using conditional logic. Everything is shown using the LIST command so those with access to older hardware like this can follow along. From there this quantum computer even goes as far as demonstrating a quantum full adder.

There are a number of other videos on other topics available as well. For example, there’s an AmigaBasic program that simulates quantum wave packets and a QBasic program that helps visualize the statistical likelihood of finding an electron at various locations around a hydrogen nucleus. While not likely to displace any supercomputing platforms anytime soon, it’s a good look at how you don’t need a lot of computing power in all situations. And, if you need a refresher on some of these concepts, there’s an overview on how modern quantum computers work here.

Ruined 1993 ThinkPad Tablet Brought Back From The Brink

November 18, 2024 by 10 Comments

Collecting retrocomputers is fun, especially when you find fully-functional examples that you can plug in, switch on, and start playing with. Meanwhile, others prefer to find the damaged examples and nurse them back to health. [polymatt] can count himself in that category, as evidenced by his heroic rescue of an 1993 IBM ThinkPad Tablet.

The tablet came to [polymatt] in truly awful condition. Having been dropped at least once, the LCD screen was cracked, the case battered, and all the plastics were very much the worse for wear. Many of us would consider it too far gone, especially considering that replacement parts for such an item are virtually unobtainable. And yet, [polymatt] took on the challenge nonetheless.

Despite its condition, there were some signs of life in the machine. The pen-based touch display seemed to respond to the pen itself, and the backlight sort of worked, too. Still, with the LCD so badly damaged, it had to be replaced. Boggling the mind, [polymatt] was actually able to find a 9.4″ dual-scan monochrome LCD that was close enough to sort-of fit, size-wise. To make it work, though, it needed a completely custom mount to fit with the original case and electromagnetic digitizes sheet. From there, there was plenty more to do—recapping, recabling, fixing the batteries, and repairing the enclosure including a fresh set of nice decals.

The fact is, 1993 IBM ThinkPad Tablets just don’t come along every day. These rare specimens are absolutely worth this sort of heroic restoration effort if you do happen to score one on the retro market. Video after the break.

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Atari’s Pac-Man Flop: How A Classic Went Off-Course

October 25, 2024 by 35 Comments

For fans of retro games, Pac-Man is nothing short of iconic—a game so loved it’s been ported to nearly every console imaginable. But the Atari 2600 version, released in 1982, left players scratching their heads – as laid out in a video by [Almost Something]. Atari had licensed Pac-Man to ride the wave of its arcade success, but the home version, programmed solely by [Todd Fry], missed the mark, turning an arcade icon into a surprising lesson in over-ambitious marketing.

Despite the hype, [Fry] faced an almost impossible task: translating Pac-Man’s detailed graphics and complex gameplay to the Atari’s limited 4 K cartridge with only 128 bytes of RAM. Atari’s strict limitations on black backgrounds and its choice to cut costs by sticking with a 4 K cartridge left the game barely recognizable. The famous pellet-chomping maze became simpler, colors were changed, and the iconic ghosts—reduced to single colors—flickered constantly. And then, Atari went all in, producing twelve million copies, betting on the success of universal appeal. In a twist, Pac-Man did sell in record numbers (over seven million copies) but still fell short of Atari’s expectations, leaving millions of unsold cartridges eventually dumped in a New Mexico landfill.

This debacle even kind of marked Atari’s 1983 decline. Still, Pac-Man survived the hiccup, evolving and outlasting its flawed adaptation on the 2600. If you’re interested in learning more about the ins and outs of game ports, check out the fantastic talk [Bob Hickman] gave during Supercon 2023.

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