The 6809 8-Bit Microcomputer: A Father-Son Odyssey

December 6, 2024 by Heidi Ulrich 22 Comments

If you’re nostalgic for the golden age of microprocessors and dream of building your own computer, this story might spark your imagination. [Eric Lind], passionate retro enthusiast and his 14-year-old son, embarked on a mission to craft a microcomputer from scratch, centred around the exotic Motorola 6809 chip: the µLind.

What sets this project apart is its ambition: bridging retro computing with modern enhancements. Starting with just a 6809 and some basic peripherals, the men designed a multi-stage roadmap to realize their dream. Each stage brought new challenges: debugging an address decoder, reworking memory management, and evolving glue logic into programmable GAL chips. Fascinatingly, the project isn’t just about nostalgia—it’s a playground for exploring multitasking operating systems and pushing the boundaries of 8-bit computing.

Their creativity shines in solutions like a C64-compatible joystick port, add-on expansion cards, and a memory overkill of 1MB RAM. With every setback—a missing pull-up resistor or a misrouted IRQ signal—their determination grew stronger. By combining old-school know-how with modern tools like KiCad, they’ve created something that is both personal and profoundly inspiring.

[Eric]’s hope and goal is to establish a community of people that want to expand beyond the traditional Z80 and 6502 based SBC’s. Interested? Read [Eric]’s project log on Hackaday.io and start crafting!

A Deep Dive Into A 1980s Radio Shack Computer Trainer

February 26, 2024 by Dan Maloney 17 Comments

For those of us who remember Radio Shack as more than just an overpriced cell phone store, a lot of the nostalgia for the retailer boils down to the brands on offer. Remember the Realistic line of hi-fi and stereo gear? How about Archer brand tools and parts? Patrolman scanners, Micronta test instruments, and don’t forget those amazing Optimus speakers — all had a place in our development as electronics nerds.

But perhaps the most formative brand under the Radio Shack umbrella was Science Fair, with a line of kits and projects that were STEM before STEM was a thing. One product that came along a little too late for our development was the Science Fair Microcomputer Trainer, and judging by [Michael Wessel]’s deep dive into the kit, we really missed the boat. The trainer was similar to the earlier “100-in-1”-style breadboarding kits, with components laid out on a colorful cardboard surface and spring terminals connected to their leads, making it easy to build circuits using jumper wires. The star of the show in the microcomputer trainer was a Texas Instruments TMS1100, which was a pretty advanced chip with a 4-bit CPU with its own ROM and RAM as well as a bunch of IO lines. The trainer also sported a peppy little 400-kHz crystal oscillator clock, a bunch of LEDs, a seven-segment display, a speaker, and a rudimentary keyboard.

The first video below is a general introduction to the trainer and a look at some basic (not BASIC) programs. [Michael] also pulls out the oscilloscope to make some rough measurements of the speed of the TMS1100, which turns out to be doing only about 400 instructions per second. That’s not much, but in the second video we see that it was enough for him to nerd-snipe his collaborator [Jason] into coding up an 80-nibble Tower of Hanoi solver. It’s a little awkward to use, as the program runs in spurts between which the user needs to check memory locations to see which disc to move to which peg, but it works.

It looks like people are rediscovering the Microcomputer Trainer all of a sudden. It might be a good time to pick one up.

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Computers For Fun

March 11, 2023 by Elliot Williams 9 Comments

The last couple years have seen an incredible flourishing of the cyberdeck scene, and probably for about as many reasons as there are individual ’deck designs. Some people get really into the prop-making, some into scrapping old tech or reusing a particularly appealing case, and others simply into the customization possibilities. That’s awesome, and they’re all different motivations for making a computer that’s truly your own.

But I really like the motivation and sentiment behind [Andreas Eriksen]’s PotatoP. (Assuming that his real motivation isn’t all the bad potato puns.) This is a small microcomputer that’s built on a commonly available microcontroller, so it’s not a particularly powerful beast – hence the “potato”. But what makes up for that in my mind is that it’s running a rudimentary bare-metal OS of his own writing. It’s like he’s taken the cyberdeck’s DIY aesthetic into the software as well.

What I like most about the spirit of the project is the idea of a long-term project that’s also a constant companion. Once you get past a terminal and an interpreter – [Andreas] is using LISP for both – everything else consists of small projects that you can check off one by one, that maybe don’t take forever, and that are limited in complexity by the hardware you’re working on. A simple text editor, some graphics primitives, maybe a sound subsystem. A way to read and write files in flash. I don’t love LISP personally, but I love that it brings interactivity and independence from an external compiler, making the it possible to develop the system on the system, pulling itself up by its own bootstraps.

Pretty soon, you could have something capable, and completely DIY. But it doesn’t need to be done all at once either. With a light enough computer, and a good basic foundation, you could keep it in your backpack and play “OS development” whenever you’ve got the free time. A DIY play OS for a sandbox computing platform: what more could a nerd want?

This Snappy 8-Bit Microcomputer Brings The Speed To Retrocomputing

October 21, 2022 by Dan Maloney 45 Comments

When the need for speed overcomes you, thoughts generally don’t turn to 8-bit computers. Sure, an 8-bit machine is fun for retro gameplay and reliving the glory days, and there certainly were some old machines that were notably faster than the others. But raw computing power isn’t really the point of retrocomputing.

Or is it? [Bernardo Kastrup] over at The Byte Attic has introduced an interesting machine called the Agon Light, an 8-bit SBC that’s also a bit like a microcontroller. The machine has a single PCB that looks about half as big as an Arduino Uno, and sports some of the same connectors and terminals around its periphery. The heart of the Agon Light is an eZ80 8-bit, 18.432 MHz 3-stage pipelined CPU, which is binary compatible with the Z80. It also has an audio-video coprocessor, in the form of an ESP32-Pico-D4, which supports a 640×480 64-color display and two mono audio channels. There’s no word we could find of whether the ESP32’s RF systems are accessible; it would be nice, but perhaps unnecessary since there are both USB ports and a PS/2 keyboard jack. There’s also a pin header for 20 GPIOs as well as I2C, SPI, and UART for serial communication.

The lengthy video below goes into all the details on the Agon Light, including the results of benchmark testing, all of which soundly thrash the usual 8-bit suspects. The project is open source and all the design files are available, or you can get a PCB populated with all the SMD components and just put the through-hole parts on. [Bernardo] is also encouraging people to build and sell their own Agon Lights, which seems pretty cool too. It honestly looks like a lot of fun, and we’re looking forward to seeing what people do with this.

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The First Microcomputer: The Q1

September 28, 2022 by Jonathan Bennett 52 Comments

Quiz time, what was the first commercially available microcomputer? The Altair 8800? Something obscure like the SCELBI? The Mark-8 kit? According to [The Byte Attic], it was actually the Q1, based on the Intel 8008 processor. The first Q1 microcomputer was delivered in December of 1972, making it the first, as far as he can tell. Later revisions used the Z80 processor, which is the model pictured above that [The Byte Attic] has in his possession. It’s a beautiful little machine, with a striking orange plasma display.

The irony is that this machine is almost entirely forgotten about. The original unit may have looked more like a typewriter, pictured here. If you have any first hand knowledge, or especially software, documentation, or surviving hardware bits, make sure to check in to add to the knowledge pool about this amazing little machine.

It’s an important milestone, and the development of the Q1 may have been a direct cause of Intel developing the more powerful 8080 microprocessor. It seems that Daniel Alroy’s work on this machine literally kicked off the microcomputer revolution, and it’s been missing from our computer lore for too many years. We’re very hopeful to see more of this story come together, and the history of the Q1 fully recovered.

And if retro hardware is your jam, we’ve got you covered, including among others, the parallel story about the first microprocessor.

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Inputs Of Interest: Canadian MCM/70 Was Kinda Like The First Cyberdeck

February 23, 2022 by Kristina Panos 30 Comments

Not to start a debate in the comments or anything, but what would you say was the first microcomputer, or personal computer? We suppose the answer depends on your definition. Some would argue that the PC was born at Xerox PARC with a curious portrait-mode display and a three-button mouse, while others would say it all began in a garage in either Los Altos, California or Albuquerque, New Mexico.

If you take the term ‘computer’ to mean that which can crunch big numbers fairly quickly, then the Canadian-made MCM/70 is arguably the first personal computer in that it is portable, has an alphanumeric keyboard, a display, and supports cassette storage, which could be used to extend the 8K of memory. It was an all-in-one computing solution, and it could have an optional telephone modem built in. This was a forward-thinking machine for 1974.

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Customisable Micro-Coded Controller Helps With In-Circuit Debugging

December 30, 2021 by Dave Rowntree No comments

Over on Hackaday.io, [Zoltan Pekic] has been busy building a stack of tools for assisting with verifying and debugging retro computing applications. He presents his take on using Intel hex files for customised in-circuit testing, which is based upon simple microcoded sequencers, which are generated automatically from a high level description.

The idea is that it is very useful to be able to use an FPGA development board to emulate the memory bus component of the CPU, allowing direct memory access for design validation purposes. This approach will also allow the production of a test rig to perform board level verification. The microcode compiler (MCC) generates all the VHDL, and support files needed to target a Xilinx FPGA based dev board, but is generic enough to enable targeting other platforms with a little adaptation.

Another interesting use case enables in-circuit tracing of buggy memory accesses, with the microcode sequencer decoding the accesses and dumping the relevant information out to either a serial port, or even direct to an embedded VGA controller, hardware allowing.

This automated approach to generating customisable microcoded hardware is a very nice trick to have in your bag, and even if it only helps in certain circumstances, [Zoltan] notes that it at least serves as an interesting example of the architecture of computers from history, if not much else.

Source for the example 8085 project can be found on the project GitHub, and the toolchain source can found here also.

For an interesting practical use of microding to implement emulations of historical hardware, checkout this neat switchable reproduction calculator project.