[ZXGuesser] has pulled off a true feat of Meccano engineering: building a Meccano Hellschreiber machine. The design is a close replica of the original Siemens Feld-Hell machine as documented here. What is Hellschreiber, you might ask? It’s a very neat method of sending written messages over the air by synchronizing a printing wheel on the receiving end with pulses generated on the transmitter. By quickly moving the print wheel up and down, arbitrary figures can be printed out. If you want to learn more about Hellschreiber, check out this excellent Hackaday post from almost a decade ago!

The Mastodon thread linked above goes into more detail about the difficulty in building this behemoth — and the slight regret of sticking with the authentic QWERTZ keyboard layout! In order to use the Hellschreiber mode, you have to keep up a steady rhythm of typing at about 2.5 characters per second, otherwise, the receiving end will see randomly spaced gaps between each letter. So while having to type at a steady speed [ZXGuesser] also had to work with a slightly different keyboard layout. Despite this difficulty, some very good quality output was generated!

Incredibly, the output looks just like the output from the original, century-old design. We think this is an absolutely incredible accomplishment, and we hope [ZXGuesser] doesn’t follow through on disassembling this amazing replica — or if they do, we hope it’s documented well enough for others to try their hand at it!

Thanks [BB] for the tip!

It’s a constant battle for musicians — how to practice your instrument without bothering those around you? Many of us live in apartments or shared accommodation, and having to wait until the apartment is empty or only being able to practice at certain times of day can be restrictive, especially if you need to practice for an upcoming gig or if the creative juices start flowing and it’s 3 AM! [Gavin] was having this issue and started developing Porter, a guitar/bass practice device which works with all effects pedals and is portable and rechargeable. So you can grind away your epic heavy metal solo no matter the time of day!

While there have been similar solutions, many musicians weren’t satisfied with the sound and often couldn’t support inputs from distortion pedals. They usually chewed through batteries and were just not a great solution to the problem. [Gavin] has spent the last two years fine-tuning the design. It’s a fully analog design, with built-in rechargeable batteries to boot. So it not only sounds great, but it can last as long as your practice session does with a 15-hour runtime when fully charged!

Initially, the project began as a headphone amplifier but morphed into a design specifically for guitar and bass, with preamp and power amp stages and adjustable input impedance – 500kΩ for guitars and 1MΩ for bass. The latest revision also changed to a different power amp that further reduced THD and led to an even better sound. The schematics are up on the Hackaday.io project page, but [Gavin] is also hoping to do a crowdfunding campaign to get these devices out into the hands of guitarists everywhere!

The venerable Intel 486 was released in 1989 as the successor to the extremely popular Intel 386. It was the minimum recommended processor for Windows 98.  (Surprisingly, the Windows 95 minimum was a 386!)  But by the time XP rolled around, you needed at least a 233 MHz Pentium to install. Or at least that was the case until recently when an extremely dedicated user on MSFN named [Dietmar] showed how he hacked the XP kernel so it could run on the classic chip!

The biggest issue preventing XP from working on earlier processors is an instruction introduced on the Pentium: CMPXCHG8B. This instruction compares two 8-byte values and takes different actions depending on an equality test. It either copies the 8 bytes to a destination address or loads it into a 64-bit register. Essentially, it does what it says on the tin: it CoMPares and eXCHanGes some values. If you want to dig into the nitty-gritty details, you can check out this info on the instruction taken from the x86 datasheet.

Without getting too technical, know that this instruction is vital for performance when working with large data structures. This is because one instruction moves 8 bytes at a time, unlike the older CMPXCHG instruction, which only moves a single byte. Essentially, [Dietmar] had to find every usage of CMPXCHG8B and replace it with an equivalent series of CMPXCHG instructions.

On a side note, the once well-known and devastating Pentium F00F bug was caused by a faulty encoding of the CMPXCHG8B instruction. This allowed any user, even unprivileged users, to completely lock up a system, requiring a full reset cycle!

So [Dietmar] was successful, and now you can run the German version of Windows XP on either a real 486 or an emulated one. The installer is available on the Internet Archive and there’s a detailed video below demonstrating installing it on the 86Box virtual machine host.

Thanks to [DosFox] for the tip!

We’re big fans of calculators, computers and vintage magazines, so when we see something at the intersection of all three we always take a look. Back in 1966, Electronics Illustrated included instructions in their November issue on building, in their words, a “Space-Age Decimal Computer!” using neon lamps, a couple of tubes, and lots of soldering. The article starts on page 39 and it’s made fairly clear that it will be an expensive and complicated project, but you will be paid back many times over by the use and experience you will get!

Our modern idea of a computer differs greatly from the definitions used in the past. As many readers likely know, “Computer” was actually a job title for a long time. The job of a computer was to sit with pen, paper, and later on electromechanical devices, and compute and tabulate long lists of numbers. Imagine doing payroll for large companies completely by hand, every month. The opportunity for errors was large and was just part of doing business. As analog and later transistor-based computers started to be developed, they replaced the jobs of human computers in calculating and tabulating numbers. This is why IBM was originally called the Computing, Recording and Tabulating Company!

So at the time this article was written, the idea of a computer as just a number-cruncher meant that for the magazine readers, a machine that could add, subtract, multiply and divide was for all intents a computer. The kit is a fairly clever but simple machine. A rotary telephone dial is used to enter numbers from 1 to 10 (with the 0 acting as 10). This sends pulses into a series of boards that represent decimal decades from 1s all the way up to 100000s. You use a rotary switch to select which decade to enter a number into. And then, just like manual addition, you dial in the second number, working from the units upwards. All carries are done automatically, and you have your result after entering each addend.

As the machine can only count upwards, subtraction is done by adding complements. This is all based on doing the 9s complement of the number to be subtracted, and the article goes into a lot of detail on the operation of the machine. Tricks like these were common when using electromechanical machines and would have been familiar at the time to many readers. Of course, multiplication and division are repeated additions or subtractions, and with long inputs, it could become very tedious. However, as long as the machine was carefully constructed and each number carefully noted down, it could be a very useful tool that would eliminate errors!

Thanks to [Stephen] for the tip!

Synth designers [Erica Synths] have devised a very cool, approachable way to get started with DIY synth hacking. Designed around a breadboard, the EDU DIY LABOR is a synth module with everything you need to get started. The Basic version comes with potentiometers, switches, and jack sockets, and is aimed more at those who likely already have a decent supply of parts on hand for experimentation. The Full kit comes with all that, plus a supply of resistors, capacitors, ICs and transistors so you can get up to speed, even as a beginner.

The device is supplied as a semi-DIY kit, with some soldering and assembly required. The kit was designed in collaboration with Dr. Shalom D. Ruben, a teaching professor of engineering at the University of Colorado. So it should be approachable for those with some soldering experience under their belt. Labor includes a multi-voltage power supply which supplies all Eurorack voltages, an oscillator section for both audible ranges and LFO, a full envelope control section, an output amplifier and more! Once assembled you can quickly start making bloops, beeps, and bzzts. You can easily design filters, oscillators, amplifiers, sequencers, and whatever else you can dream up!

However, the kit is designed to be more than just a synth playground – the idea was also to create an environment where you could learn the basics of electronics at the same time, in an approachable, fun way. This is reflected in the excellent user manual, which goes beyond just assembling the device and gives some example circuits, complete with wave diagrams and detailed working explanations. Great for beginners and experienced hackers who want to learn more about fundamentals and audio synthesis!

Developer [frntc] has recently come up with a smaller and less expensive way to not only replace the SID chip in your Commodore 64 but to also make it a stereo SID! To top it off, it can also hold up to 16 games and launch them from a custom menu. The SIDKick Pico is a simple board with a Raspberry Pi Pico mounted on top. It uses a SID emulation engine based on reSID to emulate both major versions of the SID chip — both the 6581 and the 8580. Unlike many other SID replacements, the SIDKick Pico also supports mouse and paddle inputs, meaning it replaces all functionality of the original SID!

Sound can be generated in three different ways: either using PWM to create a mono audio signal that is routed out via the normal C64/C128 connectors, an external PCM5102A DAC board, or using a different PCB design that has pads for an on-board DAC and TL072 op-amp. While many Commodore purists dislike using replacement chips, the reality is that all extant SID chips were made roughly 40 years ago, and as more and more of them fail, options like the SIDKick Pico are an excellent way to keep the sound of the SID alive.

If you want to hear the SIDKick Pico in action, you can check out the samples on the linked GitHub page, or check out the video below by YouTuber Wolfgang Kierdorf of the RETRO is the New Black channel. To get your hands on a SIDKick Pico, you can follow the instructions on the GitHub page for ordering either bare PCBs or pre-assembled PCBs from either PCBWay or your board manufacturer of choice.

Thanks [Stephen] for the tip.