Multi-Divi book with hand thumbing through it

Math, Optimized: Sweden’s Maximal Multi-Divi

March 28, 2025 by Heidi Ulrich 24 Comments

Back in the early 1900s, before calculators lived in our pockets, crunching numbers was painstaking work. Adding machines existed, but they weren’t exactly convenient nor cheap. Enter Wilken Wilkenson and his Maximal Multi-Divi, a massive multiplication and division table that turned math into an industrialized process. Originally published in Sweden in the 1910’s, and refined over decades, his book was more than a reference. It was a modular calculating instrument, optimized for speed and efficiency. In this video, [Chris Staecker] tells all about this fascinating relic.

What makes the Multi-Divi special isn’t just its sheer size – handling up to 9995 × 995 multiplications – but its clever design. Wilkenson formatted the book like a machine, with modular sections that could be swapped out for different models. If you needed an expanded range, you could just swap in an extra 200 pages. To sell it internationally, just replace the insert – no translation needed. The book itself contains zero words, only numbers. Even the marketing pushed this as a serious calculating device, rather than just another dusty math bible.

While pinwheel machines and comptometers were available at the time, they required training and upkeep. The Multi-Divi, in contrast, required zero learning curve – just look up the numbers for instant result. And it wasn’t just multiplication: the book also handled division in reverse, plus compound interest, square roots, and even amortizations. Wilkenson effectively created a pre-digital computing tool, a kind of pocket calculator on steroids (if pockets were the size of briefcases).

Of course, no self-respecting hacker would take claims of ‘the greatest invention ever’ at face value. Wilkenson’s marketing, while grandiose, wasn’t entirely wrong – the Multi-Divi outpaced mechanical calculators in speed tests. And if you’re feeling adventurous, [Chris] has scanned the entire book, so you can try it yourself.

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Take A Little Bit Of Acorn To Work

March 28, 2025 by Jenny List 5 Comments

When we think of 8-bit computers, it’s natural to start with home computers. That’s where they live on in the collective memory. But a Z80, a 6502, or similar was more likely to be found unseen in a piece of industrial machinery, doing the job for which we’d today reach for a microcontroller. Sometimes these two worlds intersected, and thus we come to the EuroBEEB, a derivative of Acorn’s BBC Micro on a Eurocard. [Steve Crozier] has performed extensive research into this system and even produced a recreated PCB, providing a fascinating window into embedded computing in the early 1980s.

The EuroBEEB was the work of Control Universal, a Cambridge-based company specialising in embedded computers. They produced systems based upon 6502 and 6809 processors, and joining their product line to the then-burgeoning BBC Micro ecosystem would have been an obvious step. The machine itself is a Eurocard with a simple 6502 system shipped with ACORN BBC Basic on ROM, and could be seen as a cut-down BBC Micro with plenty of digital I/O, accesible through a serial port. It didn’t stop there though, as not only could it export its graphics to a “real” BBC Micro, it had a range of expansion Eurocards that could carry the missing hardware such as analogue input, Teletext, or high-res graphics.

The reverse-engineered PCB comes from analysis of surviving schematics, and included a couple of gate array logic chips to replace address decoding ROMs in the original. If it seems overkill for anyone used to a modern microcontroller, it’s worth remembering that by the standards of the time this was a pretty simple system. Meanwhile if you only fancy trying BBC BASIC, there’s no need to find original hardware.

Pi Pico Turns Atari 2600 Into A Lo-fi Photo Frame

March 27, 2025 by Jenny List 7 Comments

The cartridge based game consoles of decades ago had a relatively simple modus operandi — they would run a program stored in a ROM in the cartridge, and on the screen would be the game for the enjoyment of the owner. This made them simple in hardware terms, but for hackers in the 2020s, somewhat inflexible. The Atari 2600 is particularly troublesome in this respect, with its clever use of limited hardware making it not the easiest to program at the best of times. This makes [Nick Bild]’s Atari 2600 photo frame project particularly impressive.

The 2600 has such limited graphics hardware that there’s no handy frame buffer to place image data into, instead there are some clever tricks evolved over years by the community to build up bitmap images using sprites. Only 64 by 84 pixels are possible, but for mid-70s consumer hardware this is quite the achievement.

In the case of this cartridge the ROM is replaced by a Raspberry Pi Pico, which does the job of both supplying the small Atari 2600 program to display the images, and feeding the image data in a form pre-processed for the Atari.

The result is very 8-bit in its aesthetic and barely what you might refer to as photos at all, but on the other hand making the Atari do this at all is something of a feat. Everything can be found in a GitHub repository.

If new hardware making an old console perform unexpected tricks is your bag, we definitely have more for you.

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The Vectrex Home Computer You Never Had

March 25, 2025 by Jenny List 15 Comments

The Vectrex console from the early 1980s holds a special place in retrocomputing lore thanks to its vector display — uniquely for a home system, it painted its graphics to the screen by drawing them with an electron beam, instead of scanning across a raster as a TV screen would. It thus came with its own CRT, and a distinctive vertical screen form factor.

For all that though, it was just a games console, but there were rumors that it might have become more. [Intric8] embarked on a quest to find some evidence, and eventually turned up what little remains in a copy of Electronic Games magazine. A keyboard, RAM and ROM expansion, and a wafer drive were in the works, which would have made the Vectrex a quirky equal of most of what the likes of Commodore and Sinclair had to offer.

It’s annoying that it doesn’t specify which issue of the magazine has the piece, and after a bit or browsing archive.org we’re sorry to say we can’t find it ourselves. But the piece itself bears a second look, for what it tells us about the febrile world of the 8-bit games industry. This was a time of intense competition in the period around the great console crash, and developers would claim anything to secure a few column inches in a magazine. It’s not to say that the people behind the Vectrex wouldn’t have produced a home computer add-on for it if they could have done, but we remember as teenagers being suckered in by too many of these stories. We still kinda want one, but we’d be surprised if any ever existed.

If you have a Vectrex, it’s possible to give it a light pen.

Ancient Pocket Computer Gets A Serious Serial Upgrade

March 25, 2025 by Lewin Day 8 Comments

[Robert’s Retro] is one of those great YouTube channels that shows us the ins and outs of old and obscure computers. [Robert] likes going a step beyond the traditional teardown though, repairing and upgrading these old machines. His latest project involves giving the ZEOS Pocket PC a fully-functional serial port.

If you’re unfamiliar with the ZEOS Pocket PC, you might know it as the Tidalwave PS-1000—it’s a pretty straightforward clone. Originally, these machines could be had with a proprietary serial adapter to enable them to interface with external peripherals. However, like most obscure cables and connectors from three decades ago, they’re virtually unobtainable today.

To solve this problem, [Robert] decided to hack in a traditional DE-9 connector instead. Commonly referred to as the DB-9, this is the most common serial port design used on IBM PCs and compatibles. Getting the larger port into the compact PC required some careful hacking of the case, as well as delicate soldering to hook up the pins to the right signals on the tightly-packed motherboard. This video does involve cutting some vintage plastic, but overall it’s a very neat mod that is handled with due respect and care.

This isn’t the first time we’ve seen him upgrade a classic portable computer, either.

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Handheld Console Plays Original Pong With Modern E-Waste

March 24, 2025 by Donald Papp 8 Comments

[Simon] wrote in to let us know about DingPong, his handheld portable Pong console. There’s a bit more to it than meets the eye, however. Consider for a moment that back in the 1970s playing Pong required a considerable amount of equipment, not least of which was dedicated electronics and a CRT monitor. What was huge (in more than one way) in the 70s has been shrunk down to handheld, and implemented almost entirely on modern e-waste in the process.

The 1970s would be blown away by a handheld version of Pong, made almost entirely from salvaged components.

DingPong is housed in an old video doorbell unit (hence the name) and the screen is a Sony Video Watchman, a portable TV from 1982 with an amazing 4-inch CRT whose guts [Simon] embeds into the enclosure. Nearly everything in the build is either salvaged, or scrounged from the junk bin. Components are in close-enough values, and power comes from nameless lithium-ion batteries that are past their prime but still good enough to provide about an hour of runtime. The paddle controllers? Two pots (again, of not-quite-the-right values) sticking out the sides of the unit, one for each player.

At the heart of DingPong one will not find any flavor of Arduino, Raspberry Pi, or ESP32. Rather, it’s built around an AY-3-8500 “Ball & paddle” (aka ‘Pong’) integrated circuit from 1977, which means DingPong plays the real thing!

We have seen Pong played on a Sony Watchman before, and we’ve also seen a vintage Pong console brought back to life, but we’re pretty sure this is the first time we’ve seen a Sony Watchman running Pong off a chip straight from the 70s. Watch it in action in the video (in German), embedded below.

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The Mysterious Mindscape Music Board

March 23, 2025 by Maya Posch 11 Comments

Sound cards on PC-compatible computer systems have a rather involved and convoluted history, with not only a wide diversity of proprietary standards, but also a collection of sound cards that were never advertised as such. Case in point the 1985 Mindscape Music Board, which was an add-on ISA card that came bundled with [Glen Clancy]’s Bank Street Music Writer software for IBM PC. This contrasted with the Commodore 64 version which used the Commodore SID sound chip. Recently both [Tales of Weird Stuff] and [The Oldskool PC] on YouTube both decided to cover this very rare soundcard.

Based around two General Instruments AY-3-8913 programmable sound generators, it enabled the output of six voices, mapped to six instruments in the Bank Street Music Writer software. Outside of this use this card saw no use, however, and it would fade into obscurity along with the software that it was originally bundled with. Only four cards are said to still exist, with [Tales of Weird Stuff] getting their grubby mitts on one.

As a rare slice of history, it is good to see this particular card getting some more love and attention, as it was, and still is, quite capable. [The Oldskool PC] notes that because the GI chip used is well-known and used everywhere, adding support for it in software and emulators is trivial, and efforts to reproduce the board are already underway.

Top image: Mindscape Music Board (Credit: Ian Romanick)

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