Replacement PCB Replicates Early 80s Modem

It’s certainly been a few decades, but plenty of us remember a time before widespread access to broadband internet, when connections were generally made over phone lines using acoustic modems. In the 90s these could connect you to AOL and Napster well enough, but in the early 80s the speeds were barely enough to read text as it loaded. A company called Hayes set out to change this with some of the first useful, widely-available modems for the PCs at the time. While they couldn’t keep up with the changing times there’s still a retro community that has these antiques, and to modernize it a bit this drop-in replacement for the PCBs replicates these old modems almost exactly.

The new PCB is equipped with everything needed to get a retro computer online again, including all the ports to connect a computer without any further modifications. It houses a few modern upgrades beyond its on-board processors, though. Rather than needing an actual acoustic coupled phone, this one has an ESP32 which gives it wireless capability. But the replacement PCB maintains the look and feel of the original hardware by replicating the red status LEDs at the front, fitting into the original Hayes cases with no modifications needed at all, and even includes a small speaker through which it can replicate the various tones, handshakes, and other audio cues that those of us nostalgic for this new online era remember quite well.

For those looking for a retro feel without the hassle of getting antique networking equipment functional again, this type of upgrade that preserves the essence of the original hardware is an excellent way of keeping retro computers functional on modern networking equipment. But if you absolutely must get the networking equipment exactly right down to the last patch cable, you might end up having to build your own ISP from scratch.

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Give Your Projects A Retro Tint With This 8051-based Arduino Uno

Most of us are familiar with the Arduino Uno, a starting place for electronics projects since 2010. But what if the Arduino Uno was released in 1980? You’d probably get something like [ElectroBoy]’s 8051-based Arduino Uno.

28-pin DIP integrated circuit with a window revealing the die
Close-up shot of the 87C752, an 8051 with EPROM

The Arduino Uno-compatible board has an MCS-51 (often called 8051 instead) instead of the usual ATmega328P/ATmega168. Specifically, [ElectroBoy] uses the AT89S52. Like the ATmega microcontrollers, the AT89S52 has an 8-bit CPU with a Harvard architecture and very similar GPIO capabilities. Unlike the ATmega, however, the original MCS-51 has a CISC CPU (as opposed to ATmega being RISC) and a release date about 36 years earlier.

The board itself also has some differences from the original Arduino Uno. First of all, it has a USB type-C port, which is definitely a bonus. Secondly, it’s simpler: No USB-UART (which also means no USB programming), a different pin layout (Arduino shields likely won’t fit) and more I/Os than the ATmegas have. Sure, it’s not as practical as an actual Arduino Uno, but it’s definitely cool for our retrocomputing nerds.

Crusty: The Story Of The Mac SE That Could

Retrocomputing often involves careful restorations, rare components, and white gloves.  This story involves none of those. This is the story of two people who sought to answer one of the greatest questions in the universe: What does it take to kill a Mac SE?

Crusty’s mainboard as found

The star of the show here is Crusty, a Mac SE that was found on the loading dock of a scrap company. It sat out in the weather for at least 6 months, complete with the original leaking lithium battery.

Enter [RadRacer203], who is friends with the owner of this particular scrap company. [RadRacer203] and picked up Crusty, along with a few other classic Macs. He brought these machines to VCF East 2021, where our other hero comes in. [CJ] is something of a magician with CRTs and analog electronics. Trained under [Sark] himself, [CJ] has mastered the 5-finger exploding capacitor technique.

The battery had eaten through the mainboard and even into the chassis. But after a thorough cleaning, the damn thing booted up. Crusty was born.

This Mac was a survivor. Much like Top Gear and their plucky Toyota Hilux, [RadRacer203] and [CJ] devised a plan to put Crusty to the test.

Click through the break for more!

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Brand-New PCB Makes Replica TRS-80 Possible

If like us, you missed out on the TRS-80 Model I back when it first came out, relax .With this brand-new PCB that’s a trace-for-trace replica of the original and a bunch of vintage parts, you can build your own from scratch.

Now, obviously, there are easier ways to enjoy the retro goodness that is the 46-year-old machine that in many ways brought the 8-bit hobby computing revolution to the general public’s attention. Sadly, though, original TRS-80s are getting hard to come by, and those that are in decent enough shape to do anything interesting are commanding top dollar. [RetroStack]’s obvious labor of love project provides the foundation upon which to build a brand new TRS-80 as close as possible to the original.

The PCB is revision G and recreates the original in every detail — component layout, connectors, silkscreen, and even trace routing. [RetroStack] even replicated obvious mistakes in the original board, like through-holes that were originally used to fixture the boards for stuffing, and some weird unused vias. There are even wrong components, or at least ones that appear on production assemblies that don’t show up in the schematics. And if you’re going to go through with a build, you’ll want to check out the collection of 3D printable parts that are otherwise unobtainium, such as the bracket for rear panel connectors and miscellaneous keyboard parts.

While we love the devotion to accuracy that [RetroStack] shows with this project, we know that not everyone is of a similar bent. Luckily there are emulators and clones you can build instead. And if you’re wondering why anyone would devote so much effort to half-century-old technology — well, when you know, you know.

Thanks to [Stephen Walters] for the tip.

Feature image: Dave Jones, CC BY-SA 4.0, via Wikimedia Commons


Bringing A Chain Printer Back To Life: The Power Supply

[Usagi Electric] has his Centurion minicomputer (and a few others) running like a top.  One feature that’s missing, though, is the ability to produce a hard copy. Now, a serious machine like the Centurion demands a serious printer. The answer to that is an ODEC-manufactured printer dressed in proper Centurion blue. This is no ordinary desktop printer, though. It’s a roughly 175lb (80 Kg) beast capable of printing 100 lines per minute. Each line is 132 characters wide, printed on the tractor-feed green bar paper we all associate with old computer systems.

This sort of printer was commonly known as a chain printer, as the letters are on a chain that rides over a series of 66 hammers. Logic on this printer is 74 series logic chips – no custom silicon or LSI (Large Scale Integration) parts on this 47-year-old monster.

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The Sol-1: A 16-bit Computer In 74HC Logic With C Compiler And Unix-like OS

Sol-1 system pictured from the front. {Credit: Paulo Constantino)
Sol-1 system pictured from the front. {Credit: Paulo Constantino)

While the concept of a computer system implemented in discrete logic ICs is by itself not among the most original ideas, the way some machines are executed certainly makes them stick out. This is the case with [Paulo Constantino]’s Sol-1, which not only looks extremely professional, but also comes with a lot of amenities that allow for system development, including a C compiler and assembler, a Unix-like OS (in development), DMA, and a whole host of interfaces to interact with the system and peripherals (serial, parallel, IDE, etc.). Not to mention a SystemVerilog model and an emulator, all of which can be found on [Paulo]’s GitHub.

More photos and videos can be found on [Paulo]’s YouTube channel, as well as the Sol-1 website, which shows off the intricate wire wrap work on the back of each PCB. In terms of the ISA, there are 5 general purpose registers (one scratch) which can also be used as two 8-bit registers each. Most operations are supported, except for floating point. For future improvements and additions, Sol-1’s OS will get more features added, and the first major software to be ported to the Sol-1 should be Colossal Cave Adventure and similar text-based adventure (dungeon) games.

Cowgol Development Environment Comes To Z80 And CP/M

Cowgol on Z80 running CP/M ties together everything needed to provide a Cowgol development environment (including C and assembler) on a Z80 running the CP/M operating system, making it easier to get up and running with a language aimed to be small, bootstrapped, and modern.

Cowgol is an experimental modern language for (very) small systems.

The Zilog Z80 was an 8-bit microprocessor common in embedded systems of the 1970s and 1980s, and CP/M was a contemporary mass-market operating system. As for Cowgol? It’s an Ada-inspired compiler toolchain and programming language aimed at very small systems, such as the Z80.

What’s different about Cowgol is that it is intended to be self-hosted on these small systems; Cowgol is written in itself, and is able to compile itself. Once one has compiled the compiler for a particular target architecture (for example, the Z80) one could then use that compiler on the target system to compile and run programs for itself.

Thankfully, there’s no need to start from scratch. The Cowgol on Z80 running CP/M repository (see the first link of this post) contains the pre-compiled binaries and guidance on using them.

Cowgol is still under development, but it works. It is a modern language well-suited to (very) small systems, and thanks to this project, getting it up and running on a Z80 running CP/M is about as easy as such things can get.

Thanks to [feinfinger] for the tip!