Get Roped Into Magnetic Core Memory With This 512 Bit Module

July 11, 2025 by Tyler August 16 Comments

Magnetic Core memory was the RAM at the heart of many computer systems through the 1970s, and is undergoing something of a resurgence today since it is easiest form of memory for an enterprising hacker to DIY. [Han] has an excellent writeup that goes deep in the best-practices of how to wire up core memory, that pairs with his 512-bit MagneticCoreMemoryController on GitHub.

Magnetic core memory works by storing data inside the magnetic flux of a ferrite ‘core’. Magnetize it in one direction, you have a 1; the other is a 0. Sensing is current-based, and erases the existing value, requiring a read-rewrite circuit. You want the gory details? Check out [Han]’s writeup; he explains it better than we can, complete with how to wire the ferrites and oscilloscope traces to explain why you want to wiring them that way. It may be the most complete design brief to be written about magnetic core memory to be written this decade.

This little memory pack [Han] built with this information is rock-solid: it ran for 24 hours straight, undergoing multiple continuous memory tests — a total of several gigabytes of information, with zero errors. That was always the strength of ferrite memory, though, along with the fact you can lose power and keep your data. In in the retrocomputer world, 512 bits doesn’t seem like much, but it’s enough to play with. We’ve even featured smaller magnetic core modules, like the Core 64. (No prize if you guess how many bits that is.) One could be excused for considering them toys; in the old days, you’d have had cabinets full of these sorts of hand-wound memory cards.

Magnetic core memory should not be confused with core-rope memory, which was a ROM solution of similar vintage. The legendary Apollo Guidance Computer used both.

We’d love to see a hack that makes real use of these pre-modern memory modality– if you know of one, send in a tip.

Four brown perf board circuits are visible in the foreground, each populated with many large DIP integrated circuits. The boards are connected with grey ribbon cable. Behind the boards a vacuum fluorescent display shows the words “DIY CPU.”

Designing A CPU With Only Memory Chips

July 11, 2025 by Aaron Beckendorf 14 Comments

Building a simple 8-bit computer is a great way to understand computing fundamentals, but there’s only so much you can learn by building a system around an existing processor. If you want to learn more, you’ll have to go further and build the CPU yourself, as [MINT] demonstrated with his EPROMINT project (video in Polish, but with English subtitles).

The CPU began when [MINT] began experimenting with uses for his collection of old memory chips, and quickly realized that they could do quite a bit more than store data. After building a development board for single-chip based programmable logic, he decided to build a full CPU out of (E)EPROMs. The resulting circuit spans four large pieces of perfboard, weighs in at over half a kilogram, and took several weeks of soldering to create. Continue reading “Designing A CPU With Only Memory Chips” →

An Emulated Stroll Down Macintosh Memory Lane

July 10, 2025 by Tyler August 6 Comments

If you’re into Macs, you’ll always remember your first. Maybe it was the revolutionary classic of 1984 fame, perhaps it was the adorable G3 iMac in 1998, or even a shiny OS X machine in the 21st century. Whichever it is, you’ll find it emulated in [Marcin Wichary]’s essay “Frame of preference: A history of Mac settings, 1984–2004” — an exploration of the control panel and its history.

Image of PowerBook showing the MacOS 8.0 desktop. — That’s not a photograph, it’s an emulator. (At least on the page. Here, it’s a screenshot.)

[Marcin] is a UI designer as well as an engineer and tech historian, and his UI chops come out in full force, commenting and critiquing Curputino’s coercions. The writing is excellent, as you’d expect from the man who wrote the book on keyboards, and it provides a fascinating look at the world of retrocomputing through the eyes of a designer. That design-focused outlook is very apropos for Apple in particular. (And NeXT, of course, because you can’t tell the story of Apple without it.)

There are ten emulators on the page, provided by [Mihai Parparita] of Infinite Mac. It’s like a virtual museum with a particularly knowledgeable tour guide — and it’s a blast, getting to feel hands-on, the design changes being discussed. There’s a certain amount of gamification, with each system having suggested tasks and a completion score when you finish reading. There are even Easter eggs.

This is everything we wish the modern web was like: the passionate deep-dives of personal sites on the Old Web, but enhanced and enabled by modern technology. If you’re missing those vintage Mac days and don’t want to explore them in browser, you can 3D print your own full-size replica, or a doll-sized picoMac.

screenshot of C programming on Macintosh Plus

Programming Like It’s 1986, For Fun And Zero Profit

July 9, 2025 by Tyler August 27 Comments

Some people slander retrocomputing as an old man’s game, just because most of those involved are more ancient than the hardware they’re playing with. But there are veritable children involved too — take the [ComputerSmith], who is recreating Conway’s game of life on a Macintosh Plus that could very well be as old as his parents. If there’s any nostalgia here, it’s at least a generation removed — thus proving for the haters that there’s more than a misplaced desire to relive one’s youth in exploring these ancient machines.

So what does a young person get out of programming on a 1980s Mac? Well, aside from internet clout, and possible YouTube monetization, there’s the sheer intellectual challenge of the thing. You cant go sniffing around StackExchange or LLMs for code to copy-paste when writing C for a 1986 machine, not if you’re going to be fully authentic. ANSI C only dates to 1987, after all, and figuring out the quirks and foibles of the specific C implementation is both half the fun, and not easily outsourced. Object Pascal would also have been an option (and quite likely more straightforward — at least the language was clearly-defined), but [ComputerSmith] seems to think the exercise will improve his chops with C, and he’s likely to be right.

Apparently [ComputerSmith] brought this project to VCS Southwest, so anyone who was there doesn’t have to wait for Part 2 of the video to show up to see how this turns out, or to snag a copy of the code (which was apparently available on diskette). If you were there, let us know if you spotted the youngest Macintosh Plus programmer, and if you scored a disk from him.

If the idea of coding in this era tickles the dopamine receptors, check out this how-to for a prizewinning Amiga demo. If you think pre-ANSI C isn’t retro enough, perhaps you’d prefer programming by card?

Continue reading “Programming Like It’s 1986, For Fun And Zero Profit” →

Software Defined Retro ROM Makes 8-bit Easy

July 5, 2025 by Tyler August 28 Comments

Like the rest of us, 8-bit hardware is not getting any newer, and failed ROMs are just a fact of life. Of course you can’t call up Commadore corporation for replacement parts anymore, so something is needed. [Peirs Rocks] wasn’t satisfied with the existing options, so he came up with the Software Defined Retro ROM to serve as a drop-in replacement for 2364, 2332, and 2316 ROM chips.

Physically, the Software Defined Retro ROM is a PCB that matches the footprint of the original ROM chip, and holds an STM32F4 family microcontroller with a number of extra pins facing upwards. Some of those pins are for programming, so you can flash the board in-situ without removing it from the system using a Pi Pico. The others pins are jumpers for image selection or chip configuration. Depending which STM32 you use, you can have upto 16 ROM images on the board, at whatever chip select behaviour you require. The ROM’s chip select lines could be configured at the factory to answer to HIGH or LOW, and this board can handle either with a jumper swap.

The documentation on the GitHub is very well done, for which we applaud [Piers]. Instructions and demos are also available in the video embedded below. We could certainly see this hack becoming popular in the retrocomputer community, especially as everything ages and memories continue to, uh, y’know. What were we talking about, again?

Oh, right, ROMs. You might think an mask ROM would last a very long time, but it’s been a very long time since some of these were made. Best to dump them while you still can. If the chip is really far gone electrically, you might try decoding a photograph of the die.

Continue reading “Software Defined Retro ROM Makes 8-bit Easy” →

A Feast Of 1970s Gaming History, And An 8080 Arcade Board

July 5, 2025 by Jenny List 2 Comments

Sometimes a write-up of a piece of retrocomputing hardware goes way beyond the hardware itself and into the industry that spawned it, and thus it is with [OldVCR]’s resurrection of a Blasto arcade board from 1978. It charts the history of Gremlin Industries, a largely forgotten American pioneer in the world of arcade games, and though it’s a long read it’s well worth it.

The board itself uses an Intel 8080, and is fairly typical of microcomputer systems from the late 1970s. Wiring it up requires a bit of detective work, particularly around triggering the 8080’s reset, but eventually it’s up and playing with a pair of Atari joysticks. The 8080 is a CPU we rarely see here.

The history of the company is fascinating, well researched, and entertaining. What started as an electronics business moved into wall games, early coin-op electronic games, and thence into the arcade segment with an 8080 based system that’s the precursor of the one here. They even released a rather impressive computer system based on the same hardware, but since it was built into a full-sized desk it didn’t sell well. For those of us new to Gremlin Industries the surprise comes at the end, they were bought by Sega and became that company’s American operation. In that sense they never went away, as their successor is very much still with us. Meanwhile if you have an interest in the 8080, we have been there for you.

Behind RadioShack’s Cheapest Computer

June 30, 2025 by Bryan Cockfield 30 Comments

In the 1980s, there was a truly staggering amount of choice for a consumer looking to purchase a home computer. On the high end, something like an Apple Lisa, a business-class IBM PC, or a workstation from Sun Microsystems could easily range from $6,000 to $20,000 (not adjusted for inflation). For the time, these mind-blowing prices might have been worth the cost, but for those not willing to mortgage their homes for their computing needs, there were also some entry-level options. One of these was the Sinclair ZX-80, which was priced at an astounding $100, which caused RadioShack to have a bit of a panic and release this version of the TRS-80 computer to compete with it.

As [David] explains in his deep dive into this somewhat obscure machine, the TRS-80 MC-10 was a commercial failure, although not for want of features. It had a color display, a chicklet keyboard, and 4K of RAM, which were all things that the ZX-80 lacked.

Unfortunately, it also had a number of drawbacks compared to some of its other contemporaries that made consumers turn away. Other offerings by Commodore, Atari, Texas Instruments, and even RadioShack themselves were only marginally more expensive and had many more features, including larger memory and better storage and peripheral options, so most people chose these options instead.

The TRS-80 MC-10 is largely a relic of the saturated 80s home computer market. It’s drop in price to below $50, and the price competition between other PC manufacturers at the time was part of the reason for the video game crash of the 1980s, and even led to Steve Jobs getting fired from Apple. There’s not a huge retro scene for these machines either, although there is at least one game developer you can see in the video below from [Spriteworx]. If you want to experiment with some of the standard TRS-80 software, there are emulators that have everything you need.