8 bit

54 Articles

Revisiting A Z80 Game From 1990

February 8, 2024 by 16 Comments

Back in the days of 8-bit computers, like no doubt many readers of similar age, we wrote little games. First in BASIC, then augmented with little machine code speed-ups. We didn’t come close to [Óscar Toledo Gutiérrez] though, who’s reverse engineering a 2K all-machine-code game he wrote back in 1990. As a tale of software archaeology it’s fascinating.

The game itself is an avoid-the-monsters platformer with plenty of ladders for the little sprite-based protagonist to run down. The computer was a Mexican homebrew educational machine with a TMS9118 display chip and an AY-3-8910 synthesizer, so the result had both color and music. His run through the code breaks it down neatly into individual sections, so it’s possible to see what’s going on without an in-depth knowledge of machine code.

He readily admits it bears all the hallmarks of an 11-year-old’s knowledge at the time, and that it has some parts less elegant, but nevertheless it’s something of an achievement at any age. It was out of date gameplay-wise in 1990 but in 1982 it could probably have been bought on a tape by eager kids. Here in 2024 he’s got it for download should you have a Colecovision or an MSX. There’s a gameplay video below the break, take a look.

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Forget The Altair! Remember The Mark-8!

December 16, 2023 by 39 Comments

Calling any one computer the first hobby computer is fraught with peril. Most people think the MITS Altair 8800, first featured in Popular Electronics back in January 1975, was the first. Some might argue that others were first, but there is no doubt that the Altair started the hobby computer revolution from a practical standpoint. However, there was another computer that almost took the crown. It, too, appeared in a magazine — Radio and Electronics. But it was in the July 1974 issue. That computer was the Mark 8, and [Artem Kalinchuk] is building a replica that you can see started in the video below. This isn’t some Arduino work-alike. He has a pile of parts and some almost authentic-looking PCBs.

The Mark 8 used the 8008, not the 8080, so it was less powerful. [Artem] has been building a replica Altair, too. Check out his YouTube channel if you are interested in those.

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The Clock, Another Way To Modify The Sound Of A Synth Chip

October 17, 2023 by 10 Comments

The Philips SAA1099 is perhaps one of the lesser-known among the crop of 1980s-era 8-bit sound generator chips, but with three stereo voices onboard it makes a capable instrument for chiptune experimentation. It’s attracted the attention of [Folkert van Heusden], who’s tried the novel experiment of seeing what happens when a sound chip’s clock is varied.

A quick search of the internet reveals that the chip, which appeared in early Sound Blaster cards, is intended to have an 8 MHz clock. He’s hooked it up to an Arduino as a variable clock source, which surprised us but it seems an ATmega328’s timer is faster than we expected.

There are a couple of WAV files, and as expected the clock frequency has a significant effect on the pitch. The samples just sweep up and down without much attempt at making a sound you’d want to hear, but it does raise an interesting possibility of adding a further pitch bending ability to the capabilities already in the chip. When these circuits were new we couldn’t control a clock on a whim with the 8-bit processors of the day, so of course none of us thought to try this at the time. He’s tried it, so you don’t have to.

The SAA1099 has been mentioned in these pages only once, as a chip used in peripherals for 1980s Czech computers.

A Virus For The BBC Micro

September 12, 2023 by 11 Comments

If you work at all with British software or hardware engineers, you’ll find that there’s an entire generation perhaps now somewhere between their mid-40s and mid-50s, who stand slightly apart from their peers in their background and experience. These were the lucky teenagers who benefited from the British government’s 1980s push to educate youngsters in computing, and who unlike those before or who followed, arrived at university engineering courses fresh from school fully conversant with every facet of a computer from the hardware upwards.

[Alan Pope] is from that generation, and he relates a tale from his youth that wasn’t so out of place back in those days, of how he wrote what we’d now call a simple virus for the BBC Micro. Better still, he’s re-created it.

The post is as much a delightful trip back through that era of microcomputing, including an entertaining aside as he shared an airline journey with BBC Micro designer Chris Turner, and it serves as a reminder of how the BBC Micro’s disk operating system worked. There was a !boot file, which was what would be run from the disk at startup, and his bit of code would subvert that and hide itself in the machine’s so-called sideways RAM. The payload was pretty simple, every 32 soft reboots it would print a “Hello world” message, but it seems that was enough back in 1989 to get him into trouble. The 2023 equivalent works, but we’re guessing no teacher will come for him this time.

If you can’t find a real BBC Micro but still want one on hardware, we’ve brought you an FPGA version in the past.

Hackaday Prize 2023: Scratch Made 8-Bit Educational Computer

May 29, 2023 by 6 Comments

To demonstrate the functionality of an 8-bit computer processor at a very basic level,  [Mazen Gomaa] assembled a Homemade 8-Bit Educational Computer using common CMOS logic chips, a handful of prototyping boards, and an impressive number of carefully connected wires. [Mazen] was inspired by Ben Eater’s 8-bit TTL Breadboard Computer but opted to solder the chips and other components onto proto boards instead of using solderless breadboards.

The 8-Bit computer is based on the Simple-As-Possible (SAP) computer architecture described in the book “Digital Computer Electronics” by [Paul Malvino] and [Jerald Brown]. These useful educational examples demonstrate data, computer logic, and even programming in the context of basic electronic components. Tinkering with such simple computers provides a real “zeros and ones” exposure to computation.

[Mazen] added some additional features and functionality to his computer, including an instruction keypad, an address keypad, a dot matrix memory data viewer, a Schottky diode matrix ROM, and a boot loader that initializes the RAM with data stored in ROM. With clock speeds up to 100 Hz, the computer consumes around 300-500 mA of current.

Future plans include expanding the memory and instruction set from the present 128-bit (8×16) RAM, 64-bit (8×8) ROM, and a set of ten instructions.  Already, this project is a great addition to an ever-growing catalog of homemade solderless breadboard computers, LCD snake games, and VGA video cards.

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Commodore 64 Upgrade In Modern Package

May 23, 2023 by 50 Comments

While the Commodore 64 was an immensely popular computer for its time, and still remains a strong favorite within the retrocomputing community, there’s a reason we’re not using modern Commodore-branded computers today. Intense competition, company mismanagement, and advancing beyond 8-bit computers too late in the game all led to the company’s eventual downfall. But if you’re still a Commodore enthusiast and always wished you were able to get an upgraded C64, you might want to take a look at the Commander X16, a modern take on this classic computer.

We’ve actually seen the Commander X16 before, but this was back in its early days of prototyping and design. This video from [Adrian’s Digital Basement], also linked below the break, takes a look at how it’s come in the four years since [David Murray] started this project. At its core, it’s an 8-bit 6502-based computer like you’d find in the 1980s but built with new components. There are some more modern updates as well such as the ability to use an SD card as well as built-in SNES controller ports, but the real magic here is the VERA module. Built around an FPGA, this module handles graphics, some of the audio, and the storage capabilities and does all of these things much better than the original Commodore, while still being faithful to what made these computer great.

While the inclusion of the FPGA might offend some of the most staunch 8-bit purists, it turns out to be necessary due to the lack of off-the-shelf video chips and really makes this build shine in the end. It’s also capable of running 6502-based software from other machines too, including the original NES. The VERA module makes it possible to run other software too, including a sample of Sonic the Hedgehog from the Sega Genesis which [Adrian] demonstrates in his video. 6502-based computers are quite versatile as the Commander X16 demonstrates, and it’s even possible to build a rudimentary 6502 on a breadboard with just a few parts.

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Pushing Crates In 8-bit Color

February 24, 2023 by 6 Comments

Moore’s law isn’t strictly holding anymore, but it is still true that most computing systems are at least trending towards lower cost over time, if not also slightly smaller size. This means wider access to less expensive hardware, even if that hardware is still an 8-bit microcontroller. While some move on to more powerful platforms as a result of this trend, there are others still fighting to push these platforms to the edge. [lcamtuf] has been working to this end, stretching a small AVR microcontroller to not only play a classic video game, but to display it on a color display. Continue reading “Pushing Crates In 8-bit Color” →