Retrocomputing

1487 Articles

Repairing An Obscure Apple II Clone

August 3, 2025 by 8 Comments

The Apple II was made in great numbers, as was the Commodore 64. But the Mimic Spartan? It was a weird Apple II clone that you needed a Commodore 64 to use. [ARC Javmaster] has found one of these obscure machines and has set about bringing it back to life. Check out the video below.

The story of the machine has been told online by one of the developers on the project, one [Brent Marykuca]. Basically, the Mimic Spartan was an Apple II clone that was intended to take advantage of a C64 as a host machine. It came in a beige box with a bunch of edge connectors and cables sticking out, and you were intended to nest it on the back of your C64 so it could hook up to all the ports. Then, you could use your machine as a C64 or an Apple II, or sort of… both… and even exchange data between both machines in some limited ways. There are also a few details of this obscure machine that have been collated by [Mike Naberezny], who is seeking the original disk that shipped with the machine when new.

It’s early days yet for [ARC Javmaster]’s efforts to restore the Mimic Spartan. Thus far, it’s had a clean and basic test. It was able to display a short line of text on a display before ceasing activity. A full boot hasn’t been achieved just yet, but we can’t wait to see where the resurrection efforts go next.

Back in the day, there were all kinds of Frankenstein computer cards that effectively put one kind of computer inside another. These days, you can condense an entire retro machine down to run on a single microcontroller.

Continue reading “Repairing An Obscure Apple II Clone” →

Rebuilt Batteries For The Cutest Clamshell At The Cafe

August 3, 2025 by 22 Comments

Keeping retrocomputers going can be tricky enough, but when you’re talking retro laptops, the battery packs add an extra challenge. While one could simply live without the battery, that’s not going to give you the full retro experience. Replacement batteries are long out of stock, so what can one do? Well, one can check out this excellent tutorial by [lazd] on rebuilding an iBook G3 Clamshell battery.

Even if you don’t have this particular laptop, the general process is likely to be similar for PC laptops of similar vintage. (Which we still can’t believe is a whole quarter-century ago.) Luckily for retrocomputer enthusiasts, even Apple used standard 18650 cells in those bygone, halcyon days when computers were allowed to be more than a few atoms thick. They do need to be unprotected, flat-top cells, but that’s easy enough to source.

So it’s really a matter of carefully prying apart the casing (apparently it needs to be Apple-branded; aftermarket cases can’t survive being opened), removing the old batteries, and welding nickel tabs onto the new cells in the proper configuration. One thing that surprised us is that, apparently, Apple did not go in for balancing in those days — so make sure your cells are all in perfect condition and all equally charged before you start, or things won’t end nicely.

As always, battery orientation matters! The cells are welded into two sets in this Clamshell iBook battery.

Assuming you can pull it off (and your battery pack’s control chip has lasted the 300 moons since its manufacture), you’ll get a not-insignificant 5-hour battery run out of what’s sure to be the cutest clamshell computer at the cafe.

If you are repairing an iBook, while you’re at it, why not upgrade the RAM? You might even be able to fix the screen if it’s succumbing to the sadly-too-common vinegar syndrome.

Exploring VersaLOGIC Pre-LSI Logic Cards With The Data/620

August 2, 2025 by 3 Comments

Before the era of large-scale integration (LSI) semiconductor circuits, discrete logic circuits using the common diode-transistor logic (DTL) were still necessary and available in a format that was modular and reusable. [David Lovett] over at the Usagi Electric farm has two great examples that date back to the 1950s and 1960s, showing the jump in technology over the course of a mere decade.

The newer Varian Data Machines 620 from 1966 uses germanium diodes and transistors, while the 1956 Bendix G-15 uses germanium diodes with vacuum tubes, the latter effectively fulfilling the same purpose as the transistors. The main difference between the modules is the density, with a decade of technological improvements allowing for more than double the logic on similarly sized cards and a similarly impressive reduction in power usage.

Currently, [David] is working on reverse-engineering these so-called VersaLogic modules to be able to troubleshoot the Data/620 machine in his possession. The results of these efforts are being published on GitHub. Although you can think of these modules as more or less big versions of the 7400-logic ICs — which began to replace them in the Data/620I from 1967 — some of the circuits on the cards get pretty complex.

Continue reading “Exploring VersaLOGIC Pre-LSI Logic Cards With The Data/620” →

Universal Control For The Last Mac You’d Ever Expect

August 1, 2025 by 8 Comments

Universal control is a neat feature on Macintosh computers, allowing you to slide your mouse seamlessly from device to device. Of course you need a relatively recent version of MacOS to make it work, right? Not necessarily– thanks to [Bart Jackobs] MacFriends, universal control has come to the Macintosh Classic.

The Arduino is perfect for this purpose, but choosing it ruined a perfectly good pun and we can never forgive that.

Well, not exactly universal control, but similar functionality at any rate. [Bart] can slide his mouse from one side of his retina display over onto the glorious 512 x 342, 1-bit display of his Macintosh Classic, just as if the 68k powered antique was a modern device. As you might expect, the Motorola 68000 in that old Mac is getting a teensy bit of help– though sadly for our love of puns, from an Arduino Nano and not any kind of Teensy.

The Arduino is emulating a mouse and keyboard on the Apple Desktop Bus using code based on the abduino by [akuker]. [Bart]’s custom software on the modern Mac captures the mouse and keyboard inputs to pipe to the Arduino via USB serial. Apple’s Universal control doesn’t require a wired connection between the two machines, of course, but then, it doesn’t work on the Classic. One could imagine redoing this project for Bluetooth communication to have that a same Clarkian feeling of technological magic Apple has always wanted to convey– but nothing was wireless in 1990 except for telegrams and a handful of telephones, so the project is appropriate as-is.

As much as we might resent that micro-controller for ruining a pun, if you want to hook into the ADB– perhaps to use old peripherals with an emulated Macintosh— an Arduino will do the job. So would a Teensy, though, and then we’d have our pun.

Our thanks to [Bart Jakobs] for the tip. Don’t forget to send in your own: the endless maw of the tipsline is always hungry.

You Can Make Your Own Floppy Drive Cleaning Disks

August 1, 2025 by 11 Comments

Once upon a time, you could buy floppy drive cleaning disks at just about any stationary or computer store. These days, they’re harder to find. If you want to build one yourself, though, you might do well to follow [Gammitin]’s fine example.

[Gammitin] has been down this road before, having built head cleaning disks before. This time, a US patent was the inspiration. It basically indicated that the spinning cleaning disc inside should be made of spunbonded polyester or spunbonded olefin (such as Dupont Tyvek)—so those materials were sought out.

The project began with [Gammitin] disassembling a standard floppy disk down to its bare components. The spindle was then separated from the magnetic platter, and refitted with a disc of Tyvek material using super glue. The disk housing was then glued back together with more super glue, and labelled as a “Floppy Cleaning Disk.” Using the disk is as simple as putting a few drops of isopropyl alcohol on the Tyvek material, and inserting it into a drive. [Gammitin] tested it with an old Olivetti machine, and found it cleaned up the heads nicely.

Sometimes, when a commercial product ceases to exist, you can just make your own at home. This is a great example of that ethos. If you’re cooking up your own tools and accessories to keep your old machines running, we’d love to hear all about it on the tipsline!

A Proper Computer For A Dollar?

August 1, 2025 by 49 Comments

When a tipster came to us with the line “One dollar BASIC computer”, it intrigued us enough to have a good look at [Stan6314]’s TinyBasRV computer. It’s a small PCB that forms a computer running BASIC. Not simply a microcontroller with a serial header, this machine is a fully functioning BASIC desktop computer that takes a PS/2 keyboard and a VGA monitor. Would that cheap price stand up?

The board uses a CH32 microcontroller, a RISC-V part that’s certainly very cheap indeed and pretty powerful, paired with an I2C memory chip for storage. The software is TinyBASIC. There’s some GPIO expandability and an I2C bus, and it’s claimed it can run in headless mode for a BASIC program to control things.

We haven’t added up all the parts in the BoM to check, but even if it’s not a one dollar computer it must come pretty close. We can see it could make a fun project for anyone. It’s certainly not the only small BASIC board out there, it’s got some competition.

Thanks [Metan] for the tip.

Soldered RAM Upgrades Finally Available For Mac-PPC

July 30, 2025 by 8 Comments

In the retrocomputing world, [DosDude1] is a name spoken with more than a little respect. He’s back again with a long-awaited hack for PowerPC Macintosh: soldered RAM upgrades!

[DosDude1] is no stranger to soldering his way to more storage– upgrading the SSD on an M4 Mac Mini, or doubling  the VRAM on an old GPU. For a PPC Mac, though, it is not enough just to solder more RAM onto the board; if that’s all it was, we’d have been doing it 20 years ago. Once the RAM is in place, you have to have some way to make sure the computer knows the RAM is in place. For a WinTel machine, getting that information to the BIOS can be as easy as plugging in the right resistors. Continue reading “Soldered RAM Upgrades Finally Available For Mac-PPC” →