A Proper OS For The Sega Genesis/Megadrive

April 3, 2025 by Jenny List 20 Comments

The console wars of the early 1990s had several players, but the battle that mattered was between Nintendo’s SNES and Sega’s Genesis, or Megadrive if you are European. They are both famous for their games, but in terms of software they can only run what’s on a cartridge. The Genesis has a Motorola 68000 on board though, which is capable of far more than just Sonic the Hedgehog. [EythorE] evidently thinks so, because here’s a port of Fusix, a UNIX-like OS, for the Sega platform.

As it stands, the OS is running on the BlastEm emulator, but given a Sega Saturn keyboard or a modified PC keyboard for the Sega, it could be run on real hardware. What you get is a basic UNIX-like OS with a working shell and the usual UNIX utilities. With 64k of memory to play with this will never be a powerhouse, but on the other hand we’d be curious to see it in a working cartridge.

Meanwhile, if the console interests you further, someone has been into its workings in great detail.

Header: Evan-Amos, CC BY-SA 3.0.

The Weird Way A DEC Alpha Boots

April 3, 2025 by Jenny List 46 Comments

We’re used to there being an array of high-end microprocessor architectures, and it’s likely that many of us will have sat in front of machines running x86, ARM, or even PowerPC processors. There are other players past and present you may be familiar with, for example SPARC, RISC-V, or MIPS. Back in the 1990s there was another, now long gone but at the time the most powerful of them all, of course we’re speaking of DEC’s Alpha architecture. [JP] has a mid-90s AlphaStation that doesn’t work, and as part of debugging it we’re treated to a description of its unusual boot procedure.

Conventionally, an x86 PC has a ROM at a particular place in its address range, and when it starts, it executes from the start of that range. The Alpha is a little different, on start-up it needs some code from a ROM which configures it and sets up its address space. This is applied as a 1-bit serial stream, and like many things DEC, it’s a little unusual. This code lives in a conventional ROM chip with 8 data lines, and each of those lines contains a separate program selectable by a jumper. It’s a handy way of providing a set of diagnostics at the lowest level, but even with that discovery the weirdness isn’t quite over. We’re treated to a run-down of DEC Alpha code encoding, and should you have one of these machines, there’s all the code you need.

The Alpha was so special in the 1990s because with 64-bit and retargetable microcode in its architecture it was significantly faster than its competitors. From memory it could be had with DEC Tru64 UNIX, Microsoft Windows NT, or VMS, and with the last of which it was the upgrade path for VAX minicomputers. It faded away in the takeover by Compaq and subsequently HP, and we are probably the poorer for it. We look forward to seeing more about this particular workstation, should it come back to life.

Australia’s Silliac Computer

April 3, 2025 by Al Williams 17 Comments

When you think about the dawn of modern computers, you often think about the work done in the UK and the US. But Australia had an early computer scene, too, and [State of Electronics] has done a series of videos about the history of computers down under. The latest episode talks about SILLIAC, a computer similar to ILLIAC built for the University of Sydney in the late 1950s.

How many racks does your computer fill up? SILLIAC had quite a few.

This episode joins earlier episodes about CSIRAC, and WREDAC. The series starts with the CSIR Mark I, which was the first computer in the southern hemisphere.

The -AC computers have a long history. While you often hear statements like, “…in the old days, a computer like this would fill a room,” SILLIAC, in fact, filled three rooms. The three meters of cabinets were in one room, the power supply in another. The third room? Air conditioning. A lot of tubes (valves, in Australia at the time) generate a lot of heat.

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Tiny Bubbles In The Memory

March 31, 2025 by Al Williams 15 Comments

We are always fascinated by bubble memory. In the late 1970s, this was the “Next Big Thing” that, as you may have guessed, was, in fact, not the next big thing at all. But there were a number of products that used it as non-volatile memory at a time when the alternative was tape or disk. [Smbakeryt] has a cool word processor with an acoustic coupler modem made by Teleram. Inside is — you guessed it — bubble memory.

The keyboard was nonfunctional, but fixable. Although we wouldn’t have guessed the problem. Bubble memory was quite high tech. It used magnetic domains circulating on a thin film of magnetic material. Under the influence of a driving field, the bubbles would march past a read-write head that could create, destroy, or read the state of the bubble.

Why didn’t it succeed? Well, hard drives got cheap and fairly rugged. The technology couldn’t compete with the high-density hard drives that could be reached with improved heads and recording strategies. Bubble memory did find use in high-vibration items, but also wound up in things like this terminal, at least one oscilloscope, and a video game.

Bubble memory evolved from twistor memory, one of several pre-disk technologies. While they are hard to come by today, you can find the occasional project that either uses some surplus or steals a part off of a device like this one.

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Protocol Analyzer Remembered

March 30, 2025 by Al Williams 22 Comments

Anyone will tell you that as hard as it is to create a working system, the real trick is making two systems talk to each other, especially if you created only one or none of them. That’s why tools that let you listen in on two systems talking are especially valuable.

If you were a well-funded lab back in the RS232 days, you might have an HP4957A protocol analyzer. The good news is that if you still use RS232, these kinds of things are now cheap on the surplus market. [IMSAI Guy] got one of these decidedly cool devices and shows it to us in the video below.

The look of these was pretty neat for their time—a folded-up instrument with a cute keyboard and a CRT-100. You can load different interpreters from ROM to RAM, such as the VT-100, which is essentially an application for the device. Of course, now you could rig one of these up in a few minutes with a PC or even a Pi Pico. But it wouldn’t have the same charm, we are sure you would agree.

You can find a lot of old RS232 gear around, from breakout boxes to advanced sniffers like this one. Too bad we couldn’t afford them when we really needed them.

This could be handy if you have a lot of ports. Either real or virtual. Or, do it yourself.

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Multi-Divi book with hand thumbing through it

Math, Optimized: Sweden’s Maximal Multi-Divi

March 28, 2025 by Heidi Ulrich 30 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.