An Ancient 8 Inch Floppy, With A PC

March 27, 2021 by Jenny List 41 Comments

Most of us may have gratefully abandoned the floppy disk a decade or more since, but even today many PCs and their operating systems retain the ability to deal with these data storage relics. The PC was widely fitted with either 5.25″ or 3.5″ disk drives, but other formats such as the older 8″ discs were not a fixture in the 16-bit desktop computing world. It’s something [Jozef Bogin] has taken aim at, with his exploits in connecting a variety of 8″ drives to a PC.

In the early 1970s there were a variety of different 8″ drive standards that weren’t all entirely compatible, but a de facto standard emerged as clones of the Shuggart drives used by IBM. It’s a modified version of this interface that can be found in a PC floppy controller. While there is enough electrical compatibility to connect the two there remains a variety of connectors used on the drives. There are also a wide range of power supplies, with drives requiring 5, 12, and 24 volts, and some of them even requiring AC mains with different versions for 50Hz and 60Hz mains frequencies.

With an 8″ drive hooked up to a PC, how might DOS, or even older Windows versions, interface with it? To that end he’s created a piece of software called 8format, which not only allows 8″ disks to be formatted for the PC, but also provides a driver that replaces the BIOS floppy settings for these drives. This doesn’t work for imaging disks from other older platforms, but he provides pointers to more capable floppy controllers for that.

If these drives interest you, there’s more to be gleaned from a tale of interfacing them with 8-bit retrocomputers.

Homebrew 68K Micro-ATX Computer Runs Its Own OS

March 27, 2021 by Tom Nardi 23 Comments

We’re no stranger to home built Motorola 68000 computers here at Hackaday, but more often than not, they tend to be an experiment in retro minimalism. The venerable processor is usually joined by only a handful of components, and there’s an excellent chance they’ll have taken up residence on a piece of perfboard. Then [NotArtyom] sent in his Blitz, and launched the bar into the stratosphere.

Make no mistake, the Blitz isn’t just some simple demo of classic chips. The open hardware motherboard has onboard floppy, IDE, and PS/2 interfaces, with a trio of 8-bit ISA expansion slots for good measure. The Motorola 68030 CPU is humming along at 50 MHz, with 4 MB of RAM and 512 KB of ROM along for the ride. Designed to fit the Micro-ATX motherboard standard, you can even mount the Blitz in a contemporary PC case and run it on a standard ATX power supply.

An earlier prototype of the Blitz motherboard.

As if the hardware wasn’t impressive enough, [NotArtyom] went ahead and created his own open source DOS-like operating system for it to run. Written in portable C, G-DOS can run on various m68k boards as well as ARM and PowerPC machines. It’s an incredible project in its own right. If you’re looking for something to show off your homebrew computer, you could certainly do worse than pulling down a copy of G-DOS. If you do port it to a new board, make sure to let [NotArtyom] know.

It’s taken [NotArtyom] three years to develop Blitz and G-DOS with his only goal being to better understand homebrew computers. He has no interest in monetizing the design or turning it into a kit, but instead hopes it will be a resource and inspiration for others with similar interests. Oh yeah, and he did all of this before he even graduated high school. If you weren’t questioning your life’s accomplishments before, now would be a great time to start.

Interested in building your own Motorola 68000 computer, but haven’t yet attained the wizarding level of [NotArtyom]? You could start with something a bit simpler like the 68k-nano, or if you’re really in a pinch, just dead bug a Dragonball 68328.

A Lockdown Brightened By A Library Of Vintage Usborne Books

March 22, 2021 by Jenny List 33 Comments

Lockdown is boring. No, let’s emphasize that, lockdown is really boring. Walking for exercise is much less fun than it was last year because it’s a wet and muddy February, and with nowhere open, a rare trip out to a McDonalds drive-through becomes a major outing. Stuck inside for the duration we turn our eyes to some of the older ways to wile away the time. Books. Remember them? In doing that I found that the friend whose house I’m living in has the whole library of Usborne children’s computer and technology books from the 1980s. Suddenly a rainy day doesn’t matter, because we’re in a cheerful world of cartoon robots and computer parts!

When Kids Learned Machine Code

A comprehensive selection to get one's teeth into. — A comprehensive selection to get one’s teeth into.

If this leaves you none the wiser, it’s worth explaining that during the 1980s home computer boom there was no Internet handily placed for finding out how your new toy worked. Instead you had to read books and hoard the scraps of information they contained. Publishers responded to this new world of technology with enthusiasm, and the British children’s publisher Usborne did so in their characteristic entertaining and informative style. For probably the only time in history, children were presented with mainstream books telling them how to write machine code and interface directly to microprocessors, and those among them who probably now read Hackaday took to them with glee. They remain something of a cult object among retrocomputing enthusiasts, and fortunately a selection of them are available for download. Usborne are still very much in business producing up-to-date books educating today’s children, and to promote some of their more recent titles for the Raspberry Pi they’ve released them in electronic form. Continue reading “A Lockdown Brightened By A Library Of Vintage Usborne Books” →

Minimal UART Computer

March 17, 2021 by Chris Lott 25 Comments

[Carsten] spent over a year developing a small CPU system, implementing his own minimalist instruction set entirely in TTL logic. The system uses a serial terminal interface for all I/O, hence the term UART in the title. [Carsten] began building this computer on multiple breadboards, which quickly got out of hand.

He moved the design over to a PCB, but he was still restless. This latest revision replaces EEPROM with cheaper and easier to use CMOS Flash chips, and the OS gains a small file system manager. As he says in the video, his enemy is feature creep.

In addition to designing this CPU project, [Carsten] built an assembler and wrote a substantial operating system and various demo programs and games. He not only learned KiCAD to make this board, but also taught himself to use an auto-router. The KiCAD design, Gerbers, and BOM are all provided in his repository above. ROM images and source code are provided, as well as a Windows cross-assembler. But wait – there’s more. He also wrote a cycle exact emulator of the CPU, which, as he rightfully brags, comes in at under 250 lines of C++ code. This whole project is an amazing undertaking and represents a lot of good work. We hope he will eventually release the assembler project as well, in case others want to take on the challenge of building it to run under Linux or MacOS. Despite this, the documentation of the Minimal UART Computer is excellent.

[Carsten] claims the project has finally passed the finish line of his design requirements, but we wonder, will he really stop here? Do check out his YouTube channel for further informative videos. And thanks to [Bruce] for sending in the tip.

Continue reading “Minimal UART Computer” →

Decoding The PS/2 Keyboard Protocol Using Good Old Fashioned Hardware

March 11, 2021 by Mike Szczys 29 Comments

1987 was a glorious year. It brought us the PS/2 keyboard standard that’s still present on many a motherboard back panel to this day. (It also marked the North America/Europe release of The Legend of Zelda but that’s another article.) Up until this point, peripherals were using DIN-5 and DE-9 (often mistakenly called DB9 and common for mice at the time) connectors or — gasp — non-standard proprietary connectors. So what was this new hotness all about? [Ben Eater] walks us through the PS/2 hall of fame by reverse-engineering the protocol.

This is a clocked data protocol, so a waveform is generated on the data pin for each key pressed that can be compared to the clock pin to establish the timing of each pulse. Every key sends a unique set of encoded pulses and voila, the whims of the user can quickly and easily be decoded by the machine.

This is where [Ben’s] dive really shines, we know he’s a breadboarding ninja so he reaches for some DIP chips. A shift register is an easy way to build up a parallel PS/2 interface for breaking out each data packet. There are a few quirks along the way, like the need to invert the clock signal so the shift register triggers on the correct edge. He also uses the propagation delay of a couple inverter gates to fire the 595 shift register’s latch pin slightly late, avoiding a race condition. A second 595 stores the output for display by a set of LEDs.

Beyond simply decoding the signal, [Ben] goes into how the packets are formatted. You don’t just get the key code, but you get normal serial interface error detection; start/stop bits and a parity bit as well. He even drills down into extended keys that send more than one packet, and a key-up action packet that’s sent by this particular keyboard.

This is the perfect low-level demo of how the protocol functions. On the practicality side, it feels a bit strange to be breaking out the serial to parallel when it would be very easy to monitor the two signal lines and decode them with a microcontroller. You might want to switch it up a bit, stick with the clock and data pins, but connect them to a Raspberry Pi using just a few passive components.

Continue reading “Decoding The PS/2 Keyboard Protocol Using Good Old Fashioned Hardware” →

Rex Wasn’t Really A PDA, It Was The First Great Digital Rolodex

March 11, 2021 by Chris Lott 32 Comments

Back in the 1990s I was fascinated with small computers. I used the HP200LX palmtop computer for almost ten years, which I wrote about back in December. Naturally, the Franklin Rex 3 PCMCIA-sized organizer caught my attention when it was released in 1997. Here was a Personal Digital Assistant (PDA) the size of a credit card that could fit not just in your pocket, but in your shirt pocket.

Viewed today, it was an interesting paradigm. The screen takes up almost the entire front face of the device with a few buttons for navigation. But isn’t it a deal-breaker that you can’t enter or edit contact info on the device itself? This was long before cellphones were pervasive, and if you had the option to connect to the internet a telephone or Ethernet cable was involved. The ability to have a large data set in your pocket viewable without slapping a brick-like laptop on a table was pretty huge.

I think the killer feature was the PCMCIA interface. I challenged myself to reverse engineer the API so that I could sync data outside of the

Continue reading “Rex Wasn’t Really A PDA, It Was The First Great Digital Rolodex” →

Full DIY: A UNIX Clone On TTL

March 9, 2021 by Jenny List 27 Comments

Making a CPU or indeed a whole computer system from scratch using discrete logic chips is by no means an unusual project, but it’s still one that requires quite a lot of technical ability and understanding of how computers work. Similarly, writing a UNIX-like operating system from scratch is something that’s been done more than once, but which definitely puts the author in an exclusive breed. Creating a CPU and computer system from discrete logic and then writing a UNIX-like OS for it? That’s definitely something new, but here’s [RobotMan2412] with both CPU and operating system to prove it!

The GR8CPU as he calls it is an 8-bit design with a 16-bit address space, making it equivalent to a typical mid-to-late 1970s 8-bit chip. He’s on revision 3 of the processor, and even makes the bold suggestion that it might be the most complex breadboard CPU ever made. That’s impressive enough, but to add a UNIX-like operating system makes it special.

While he has a real GR8CPU, it appears he’s also written an emulator with access to a disk filesystem, and it’s on this that he shows us the OS running. Don’t expect an all-singing all-dancing desktop OS here, instead it’s a kernel and very basic command line that’s just about able to run a Hello World. The kernel is hand-coded in assembler and is about 5 kB in size.

We look forward to seeing more of this project, and hope maybe he’ll one day soon publish the source. As a reminder that this is a perfectly capable platform for the job, here’s the original UNIX running on a vintage DEC PDP7.