A 3D-printed device labelled "BlixTerm" plugged into the back of a Commodore PET

BlixTerm Brings Full-Speed YouTube Video To The Commodore PET

July 1, 2022 by 13 Comments

If you’ve ever used a home computer from the late 1970s or early 1980s, you’ll no doubt be familiar with the slow speed of their user interfaces. Even listing the contents of a BASIC program from RAM could take several seconds, with the screen updating one line at a time. Video games were completely optimized for speed, but could still handle just a few slowly-moving objects at the same time. Clearly, playing anything resembling full-motion video on hardware from that era would be absolutely impossible – or so you might think.

In fact, [Thorbjörn Jemander] has managed to persuade a Commodore PET to play YouTube videos at a completely reasonable 30 frames per second. He describes the process of designing the “BlixTerm” hardware and software in his video (embedded below), along with lots of useful information on how to push digital systems to their absolute limits.

A video of a drifting car, as rendered by a Commodore PET displayNaturally, the PET needs a bit of assistance from modern hardware, in this case a Raspberry Pi Zero 2 W hooked up to the “User” expansion port. The Pi connects to YouTube through WiFi and loads the requested video, then downconverts it to a 640×200 grayscale stream and transforms each frame to an 80×25 grid of characters, using those from the PET’s ROM that most closely resemble the pattern needed.

While it took quite some effort to squeeze enough performance out of the Pi to do all of this in real time, the trickiest bit was getting the resulting character stream into the PET’s video memory fast enough. To do this, [Thorbjörn] designed a special interface card with 2 KB of dual-port SRAM, which enabled the Pi to store its video frames as soon as they were ready on one side, and the PET to load them at its own pace from the other side. With just sixteen microseconds available to process each byte, the PET’s CPU can execute only four or five machine code instructions; barely enough to load and store a single character and jump to the next memory address.

The end result, as you can see in the video, is really impressive. Even within the constraints of the Commodore character set, the resulting image is clearly recognizable, while the frame rate seems to defy the hardware’s limitations.

If you’re a Commodore aficionado and wondering what the hell that weird PET 600 model is all about, [Thorbjörn] made a video about that too; it’s a rebadged 8296 aimed at the Swedish market. We’ve actually seen a project to generate live video on the PET before, although at a much lower frame rate. Thanks for the tip, [Keith Olson]!

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Will The Real Commodore Please Stand Up?

June 16, 2022 by 27 Comments

The Commodore 64 is a much-loved 8-bit retro computer that first appeared in 1982 and finally faded away around a decade later. The Commodore company started by [Jack Tramiel] went on to make the Amiga, and eventually ceased trading some time in the late 1990s. All history, now kept alive only by enthusiasts, right? Well, not quite, as the C64 has been the subject of a number of revivals both miniature and full-sized over the years. The latest came in the form of a Kickstarter for the C64x, a seemingly legitimately-branded Commodore 64-shaped PC, but it seems that has now been paused due to a complaint from an Italian company claiming to be the real heirs of Commodore. So will the real Commodore please stand up?

The origin of the Kickstarter C64x breadbin C64 PC is well enough documented, having its roots in a legitimate 2010 offering for which the person behind the C64x appears to have gained the rights. The Italian company is also called Commodore and uses the familiar branding from the glory days to sell some Commodore-themed games, novelties, and a tablet computer, but its website is a little tight-lipped about how it came by the use of that IP. Could it have come upon those rights through the 1990s German owner of the brand, Escom? We’d be fascinated to know.

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A PCB with an Arduino Micro Pro, RCA connectors and a sub-D connector

Odd Inputs And Peculiar Peripherals: Using A Commodore Light Pen On A Modern(ish) Computer

June 11, 2022 by 8 Comments

If you worked with computers back in the 1970s, there’s a good chance you used a light pen at some point: a simple input device that you’d point at the CRT screen to highlight text, choose menu options or manipulate graphic objects. Although ubiquitous in those days, the light pen lost the battle for ergonomics to the humble mouse and was all but extinct by the late 1980s. Touchscreen styluses implement a similar function today, but touching the screen somehow doesn’t feel the same as simply pointing at it.

We therefore applaud [Maciej Witkowiak]’s efforts to bring the light pen into the 21st century by building a USB interface for a Commodore 64/128 light pen. At its heart is an Arduino Micro Pro that implements the USB HID protocol to communicate with any modern computer. It connects to the classic light pen as well as to the computer’s analog display signal and uses those to calculate the delay between the video synchronization pulses and the light pen’s output. The sync pulses are extracted from the video signal by an LM1881, a sync separator chip that will be familiar to anyone who’s worked with analog video signals.

The Arduino calculates the light pen’s position based on the measured timing intervals and reports it to the computer, using the absolute positioning mode that’s also used by things like drawing pads. [Maciej] demonstrates his system in the video embedded below, in which he uses it to operate the menus on an X window system. A great success then, although there’s one catch: light pens only work on CRT displays, so you’ll need to drag one of those big glass beasts out of storage if you want to try this yourself.

We’ve featured the Commodore light pen before in this odd gaming input device. A similar device built with a discrete LED matrix is a good illustration of the light pen’s working principle.

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A (Nearly All) New Commodore 64

May 4, 2022 by 10 Comments

The Commodore 64 remains one of the most influential of the 8-bit home computers four decades after its launch, so not surprisingly there is a huge enthusiast community surrounding it. With so many produced over the years it was available one might think that there would be no shortage of surviving specimens, but sadly time and component failure have taken their toll and the classic micro is not always the most reliable kid on the block. Thus a cottage industry has sprung up supplying C64 parts, leading [The Retro Shack] to have a go at making a new one entirely from scratch.

As you can see in the video below the break it’s not quite an entirely new ’64, as parts including some of the custom silicon come from failed boards. The PCB is a modern recreation of the original and the SID sound chip is an ARMsid though, and most of the parts come from a handy bagged-up kit that makes assembling the BoM much easier. Instead of the big silver box of the original RF modulator is a modern composite board, and there are a few issues with minor connector part differences.

Assembly is simply a very long through-hole soldering process, and once he’d completed it there was the expected refusal to work. We’ve all been there, and eventually he traced it to an incorrectly fitted chip. If you think you’ve seen a few brand new C64s here before you’d be correct, one of them even used LEGO for those elusive keycaps.

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Commodore C64: The Most Popular Home Computer Ever Turns 40

April 20, 2022 by 107 Comments

This year marks the anniversary of the most popular selling home computer ever, the Commodore 64, which made its debut in 1982. Note that I am saying “home computer” and not personal computer (PC) because back then the term PC was not yet in use for home computer users.

Some of you have probably not heard of Commodore, which is kind of sad, though there is a simple reason why — Commodore is no longer around to maintain its legacy. If one were to watch a documentary about the 1980s they may see a picture of an Apple computer or its founders but most likely would not see a picture of a Commodore computer in spite of selling tens of millions of units.

To understand the success of the C64 I would first back up and talk about the fabled era of home computers which starts with understanding the microprocessor of the day, the venerable 6502. Check out the video and follow along below.

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Commodore 64 Monitor Traces I/O Calls, Eases Debugging

February 18, 2022 by 7 Comments

Developing for the Commodore 64 can be a rewarding retrocomputing experience, and thanks to [Dave Van Wagner], things are easier with his C64 IO_Monitor project, which opens the door to logging and tracing Kernal I/O calls for closer inspection. That’s not a typo, by the way. Kernal is what handles the C64’s low-level OS routines. Amusingly, as the story goes, it did in fact originate as a misspelling of kernel, but the name stuck.

What [Dave]’s program does is trace and log all input and output calls going through Kernal, which includes just about any function one might imagine. Things like keyboard input, screen output, and disk or tape I/O are all dutifully counted and logged, allowing one to really peek under the hood at a low level when doing any kind of development work. This kind of tool has turned out to be pretty handy given [Dave]’s penchant for porting Commodore emulators to a variety of (sometimes unusual) platforms.

Interested in giving it a spin? Head to the project’s GitHub repository for all the necessary files as well as some usage details, and enjoy making debugging and development a little less opaque than it otherwise would be.

Commodore Promotional Film From 1984 Enhanced

January 29, 2022 by 10 Comments

Over on Retro Recipe’s YouTube channel, [Perifractic] has been busy restoring an old promotional video of how Commodore computers were made back in 1984 (video below the break). He cleaned up the old VHS-quality version that’s been around for years, translated the German to English, and trimmed some bits here and there. The result is a fascinating look into the MOS factory, Commodore’s German factory, and a few other facilities around the globe. The film shows the chip design engineers in action, wafer manufacturing, chip dicing, and some serious micro-probing of bare die. We also see PCB production, and final assembly, test and burn-in of Commodore PET and C64s in Germany.

Check out the video description, where [Perifractic] goes over the processes he used to clean up video and audio using machine learning. If restoration interests you, check out the piece we wrote about these techniques to restore old photographs last year. Are there any similar factory tour films, restored or not, lurking around the web? Let us know in the comments below.

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