When retro computing nostalgia meets modern wireless wizardry, you get a near-magical tap-to-load experience. It’ll turn your Commodore 64 into a console-like system, complete with physical game cards. Inspired by TapTo for MiSTer, this latest hack brings NFC magic to real hardware using the TeensyROM. It’s been out there for a while, but it might not have caught your attention as of yet. Developed by [Sensorium] and showcased by YouTuber [StatMat], this project is a tactile, techie love letter to the past.

At the heart of it is the TeensyROM cartridge, which – thanks to some clever firmware modding – now supports reading NFC tags. These are writable NTag215 cards storing the path to game files on the Teensy’s SD card. Tap a tag to the NFC reader, and the TeensyROM boots your game. No need to fumble with LOAD “*”,8,1. That’s not only cool, it’s convenient – especially for retro demo setups.

What truly sets this apart is the reintroduction of physical tokens. Each game lives on its own custom-designed card, styled after PC Engine HuCards or printed with holographic vinyl. It’s a tangible, collectible gimmick that echoes the golden days of floppies and cartridges – but with 2020s tech underneath. Watch it here.

It might be too soon to consider the innards of the old CRT monitor at the back of your closet to be something worth putting on display in your home or workshop. For that curio cabinet-worthy appeal, you need to look a bit further back. Say, about 150 years. Yes, that’ll do. A Crookes tube, the original electron beam-forming vacuum tube of glass, invented by Sir William Crookes et al. in the late 19th century, is what you need.

And a Crookes tube is what [Markus Bindhammer] found on AliExpress one day. He felt that piece of historic lab equipment was asking to be put on display in proper fashion. So he set to work crafting a wooden stand for it out of a repurposed candlestick, a nice piece of scrap oak, and some brass feet giving it that antique mad-scientist feel.

After connecting a high voltage generator and switch, the Crookes tube should have been all set, but nothing happened when it was powered up. It turned out that a capacitance issue was preventing the tube from springing to life. Wrapping the cathode end of the tube in aluminum foil, [Markus] formed what is effectively a Leyden jar, and that was the trick that kicked things into action.

As of this writing, there are no longer any Crookes tubes that we could find on AliExpress, so you’ll have to look elsewhere if you’re interested in showing off your own 19th century electron-streaming experiment. Check out the Crookes Radiometer for some more of Sir Williams Crookes’s science inside blown glass.

If you grew up with a beige Atari ST on your desk and a faint feeling of being left out once Doom dropped in 1993, brace yourself — the ST strikes back. Thanks to [indyjonas]’s incredible hack, the world now has a working port of DOOM for the Atari STe, and yes — it runs. It’s called STDOOM, and even though it needs a bit of acceleration or emulation to perform, it’s still an astonishing feat of retro-software necromancy.

[indyjonas] did more than just recompile and run: he stripped out chunks of PC-centric code, bent GCC to his will (cheers to Thorsten Otto’s port), and shoehorned Doom into a machine never meant to handle it. That brings us a version that runs on a stock machine with 4MB RAM, in native ST graphics modes, including a dithered 16-colour mode that looks way cooler than it should. The emotional punch? This is a love letter to the 13-year-old Jonas who watched Doom from the sidelines while his ST chugged along faithfully. A lot of us were that kid.

Sound is still missing, and original 8MHz hardware won’t give you fluid gameplay just yet — but hey, it’s a start. Want to dive in deeper? Read [indyjonas]’ thread on X.

Magnets aren’t magic, but sometimes you can do things with them to fool the uninitiated — like levitating. [Jonathan Lock] does that with his new maglev desk toy, that looks like at least a level 2 enchantment.

This levitator is USB-powered, and typically draws 1 W to 3 W to levitate masses between 10 g and 500 g. The base can provide 3 V to 5 V inductive power to the levitator to the tune of 10 mA to 50 mA, which is enough for some interesting possibilities, starting with the lights and motors [Jonathan] has tried.

In construction it is much like the commercial units you’ve seen: four permanent magnets that repel another magnet in the levitator. Since such an arrangement is about as stable as balancing a basketball on a piece of spaghetti, the permanent magnets are wrapped in control coils that pull the levitator back to the center on a 1 kHz loop. This is accomplished by way of a hall sensor and an STM32 microcontroller running a PID loop. The custom PCB also has an onboard ESP32, but it’s used as a very overpowered USB/UART converter to talk to the STM32 for tuning in the current firmware.

If you think one of these would be nice to have on your desk, check it out on [Jonathan]’s GitLab. It’s all there, from a detailed build guide (with easy-to-follow animated GIF instructions) to CAD files and firmware. Kudos to [Jonathan] for the quality write-up; sometimes documenting is the hardest part of a project, and it’s worth acknowledging that as well as the technical aspects.

We’ve written about magnetic levitation before, but it doesn’t always go as well as this project. Other times, it very much does. There are also other ways to accomplish the same feat, some of which can lift quite a bit more.

The fact that modern-day x86 processors still pretty much support the same operating systems and software as their ancestors did is quite a feat. Much of this effort had already been accomplished with the release of the 80386 (later 386) CPU in 1985, which was not only the first 32-bit x86 CPU, but was also backwards compatible with 8- and 16-bit software dating back to the 1970s. Making this work transparently was anything but straightforward, as [Ken Shirriff]’s recent analysis of the 80386’s main register file shows.

Using die shots of the 386’s registers and surrounding silicon, it’s possible to piece together how backwards compatibility was implemented. The storage cells of the registers are implemented using static memory (SRAM) as is typical, with much of the register file triple-ported (two read, one write).

Most interestingly is the presence of different circuits (6) to support accessing the register file for 8-, 16- or 32-bit writes and reads. The ‘shuffle’ network as [Ken] calls it is responsible for handling these distinct writes and reads, which also leads to the finding that the bottom 16 bits in the registers are actually interleaved to make this process work smoother.

Fortunately for Intel (and AMD) engineers, this feat wouldn’t have to be repeated again with the arrival of AMD64 and x86_64 many years later, when the 386’s mere 275,000 transistors on a 1 µm process would already be ancient history.

Want to dive even deeper in to the 386? This isn’t the first time [Ken] has looked at the iconic chip.

Morse code can be daunting to learn when you’re new to the game, particularly if you need it to pass your desired radio license. However, these days, there are a great many tools to aid in the learning process. A good example is the Morse Master from [Arnov Sharma].

The Morse Master is a translator for Morse code, which works in two ways. You can access it via a web app, and type in regular letters which it then flashes out as code on its in-built LEDs. Alternatively, you can enter Morse manually using the physical key, and the results will be displayed on the web app. The Morse key itself is built into the enclosure using 3D printed components paired with a Cherry-style keyboard switch. It’s perhaps not the ideal solution for fast keying, with its limited rebound, but it’s a quick and easy way to make a functional key for practice purposes. If you want to go faster, though, you might want to upgrade to something more capable. We’d also love to see a buzzer added, since Morse is very much intended as an auditory method of communication.

We’ve seen some other great Morse code trainers before, too. If you’ve trained yourself in this method of communication, don’t hesitate to share your own learning tips below.

[IMSAI Guy] grabbed an obsolete XOR gate and tried a classic circuit to turn it into a frequency doubler. Of course, being an old part, it won’t work at very high frequencies, but the circuit is super simple, just using the gate and an RC network. You can see a video of his exploration below.

The simple circuit seems like it should work, but in practice, it needed an extra component. In theory, the RC circuit acts as an edge detector. So, each edge of the input signal causes a pulse on the output as the second input lags the first.

That sounds good, but it looked terrible on the scope until a 1K resistor tied to the capacitor shifted the bias point of the gate. In all fairness, the original schematic used a Schmitt trigger gate, which may have made a difference had one been available. There were slight differences, though, depending on the type of device. An LS part, for example, didn’t need the extra resistor.

Of course, an RC network is just one way to delay the input, and the delay determines the width of the output pulse and constrains the input frequency and duty cycle. However, you could use other gates, including the other XOR gates in the package to realize a fast delay.

Frequency doublers are very common at microwave frequencies, but they don’t work in the same way. There are several ways to do it, but a common method is to use a nonlinear element to generate plenty of harmonics and then filter off everything but the second one. Or the third one, if you wanted a tripler instead.