Commodore Datassette Does Barbershop Quartet

October 20, 2023 by Kristina Panos 3 Comments

Okay, now this is just plain fun. [Linus Åkesson] modified a Commodore Datassette player to move its “mouth” and, when quadrupled, sing a clever barbershop tune called “Sweet End of Line” that’s a play on “Sweet Adeline“, a top hit from the summer of 1903.

What? Let us explain. Those with Commodore 64s who lacked disk drives often had the Datassette — a magnetic storage tape device, or cassette player used to load and save files. But they couldn’t open the doors themselves with a keypress, and they certainly couldn’t sing barbershop.

First off, [Linus] redirected the current that drives the magnetizing tape head through a speaker coil instead. Then he replaced the motor with a servo that opens the lid from the inside. A simple rubber band pulls the lid back shut. Software-wise, [Linus] is using a timer interrupt to run code that toggles the output signal, the rate of which determines the pitch.

Don’t worry — all of these modifications are reversible, so no Datassettes were truly harmed in the making. Don’t forget to check out the brief build/demo video after the break.

We’ve seen our share of tape players, but we’d never seen one with a crank until recently.

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Implementing Commodore’s IEC Bus Protocol On A KIM-1 Single Board Computer

October 7, 2023 by Maya Posch 3 Comments

Although the PET is most likely the more well-known of Commodore’s early computer systems, the KIM-1 (Keyboard Input Monitor) single board computer was launched a year prior, in 1976. It featured not only the same MOS 6502 MPU as later Commodore systems, but also an MCS6530 PIO IC that contained the ROM, RAM and programmable I/O, reminiscent of later I/O chips on Commodore systems. As the KIM-1 was only designed to be used with an external tape drive (and a terminal for fancy users), adding a floppy drive like the ubiquitous 1541 with its IEC bus interface was not a first-party accessory. How the IEC bus can be retrofitted to a KIM-1 system is demonstrated in this video by the Commodore History channel.

The Commodore KIM-1 hardware is almost directly compatible with the C64 hardware. (Credit: Commodore History on YouTube)

What is most notable is just how similar the KIM-1 hardware is to later PET and VIC hardware, with the CIA and PIO ICs featuring the same requisite pins for this purpose, and requiring only the addition of an inverting (SN7406) IC and an EPROM featuring the new code to support the proprietary Commodore IEC bus protocol, which was mostly pilfered byte-for-byte from a C64 kernal ROM.

With some creative breadboarding in place and using nothing more than the on-board LED display and keyboard matrix, it was then possible to write to the inserted floppy disk, and also to read back from it. What’s interesting here is that this essentially replaces the tape drive as target for the KIM-1, which thus retains a lot of the original functionality, but with a big performance boost. While perhaps only interesting as an academic exercise, it’s definitely an interesting look at the early beginnings of what would blossom into the Commodore 64.

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Cyanodore 6 Is A Rad Commodore 64 Synthesizer

September 29, 2023 by Lewin Day 3 Comments

The Commodore 64 is celebrated to this day for its capable SID sound chip, which provided the soundtrack for some of the best video games of its era. Even today, it’s still in demand as a chiptune synth. [gavinlyons] decided to take a breadbox-style C64 and mod it to be a more dedicated synth platform, creating what he calls the Cyanodore 6.

The build starts by equipping the C64 with MIDI via a C-LAB interface cartridge. Software is loaded on to the C64 via a readily-available SD2ISEC converter, which lets the retro computer run off SD cards. The original SID was removed and replaced with an ARMSID emulator instead, giving the rig stereo output with some custom wiring. Four potentiometers were also added to control various synth parameters by wiring them into the C64’s two joystick ports. There are a variety of synth programs that can run on the C64, with [gavinlyons] noting CynthCart, STATION64, and MicroRhythm as popular choices. Other nifty mods include the keyboard illumination, tube preamp, and integrated 7″ LCD screen.

If you’re looking to start using your C64 as a performance instrument, this build is an excellent starting point. We’ve seen other neat builds in this area before, too. It’s got just about everything you’ll need on stage. Video after the break.

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Linux On A Commodore 64

August 27, 2023 by Al Williams 30 Comments

We are used to seeing Linux running on almost everything, but we were a bit taken aback to see [semu-c64] running Linux on a Commodore 64. But between the checked-out user name and the caveat that: “it runs extremely slowly and it needs a RAM Expansion Unit”, one can already start piecing together what’s happening here.

The machine running Linux is really a RISC-V32. It just so happens that the CPU is virtual, with the C64 pretending it is a bigger machine. The boot-up appears to take hours, so this is in no way practical, even though the comment is that optimization might be able to get a 10X speed up. It would still be about as slow as you can imagine.

To further add a layer of abstraction, the code hasn’t run yet on real Commodore hardware. Instead, it is running on an emulator. The emulator has “warp” mode to run faster than a real machine, and it is still slow. So think about that before you rush out to volunteer to boot this on your real hardware.

Tricks like this fall into the talking dog category. If a dog can talk, it isn’t that you think it will have something important to say. You just marvel that it can do it at all. Still, we get it. We spend a lot of time doing things at least as pointless. But at least it is fun!

Maybe emulate the whole thing in VR? Or maybe write some virtualization code for the C64 so you can emulate a Linux box and a quantum computer simultaneously.

Quantum Computing On A Commodore 64 In 200 Lines Of BASIC

July 4, 2023 by Maya Posch 17 Comments

The term ‘quantum computer’ gets usually tossed around in the context of hyper-advanced, state-of-the-art computing devices. But much as how a 19th century mechanical computer, a discrete computer created from individual transistors, and a human being are all computers, the important quantifier is how fast and accurate the system is at the task. This is demonstrated succinctly by [Davide ‘dakk’ Gessa] with 200 lines of BASIC code on a Commodore 64 (GitHub), implementing a range of quantum gates.

Much like a transistor in classical computing, the qubit forms the core of quantum computing, and we have known for a long time that a qubit can be simulated, even on something as mundane as an 8-bit MPU. Ergo [Davide]’s simulations of various quantum gates on a C64, ranging from Pauli-X, Pauli-Y, Pauli-Z, Hadamard, CNOT and SWAP, all using a two-qubit system running on a system that first saw the light of day in the early 1980s.

Naturally, the practical use of simulating a two-qubit system on a general-purpose MPU running at a blistering ~1 MHz is quite limited, but as a teaching tool it’s incredibly accessible and a fun way to introduce people to the world of quantum computing.

A Commodore 128 with a video capture device attached

Hacking The Commodore 128 To Capture Almost Real-Time Video

July 3, 2023 by Robin Kearey 10 Comments

Although watching and editing videos may be among the primary tasks of many PCs today, it wasn’t that long ago that working with video required powerful processors and expensive video capture hardware. Even in the 1980s, home computer users were looking for ways to connect video sources to their Commodores and Ataris despite their hardware limitations. [Cameron Kaiser] has a mid-1980s consumer-grade video capture device, which he has managed to turn into an almost real-time video capture system.

A distorted video image on a C128's monitor — Allowing the graphics chip to interrupt the CPU mid-capture results in a severely distorted image

His work revolves around a device called “ComputerEyes”, a 1984-vintage hardware interface that made it possible to connect a composite video source to a home computer. The limitations of mid-1980s CPUs meant that it took around six seconds for the computer to do a quick scan of a single video frame, or a multiple of that if you wanted a higher-quality image. Another limitation, at least on Commodore machines, was that the screen had to be turned off during video capture – otherwise, the video chip would interrupt the CPU halfway through the process, causing it to lose its synchronization with the video source.

[Cameron] however, plugged his ComputerEyes into a Commodore 128. This machine, largely designed by Hackaday contributor [Bil Herd], has an unusual hardware architecture consisting of two different CPUs and, crucially, two separate video chips. The primary 8564 “VIC-II” graphics chip is used to keep compatibility with existing Commodore 64 programs, while the secondary 8563 “VDC” is mainly aimed at newer high-resolution text-based software. The VDC is also much more independent from the main system bus than the VIC-II, allowing it to display an image without disturbing the CPU.

More after the break.

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Creating A Commodore 64 Cartridge On Single-Sided Stripboard

June 30, 2023 by Maya Posch 10 Comments

The DIY Commodore 64 cartridge. (Credit: Linus Åkesson)

When you want to write software for a system like the Commodore 64, the obvious and safe choice is to create an image that can be used with a tape or floppy drive emulator. Yet these come with the obvious disadvantage of loading time and manual steps, much like with the original hardware. Unfortunately, if you crave that instant-on experience that cartridges offer – courtesy of them being plugged directly into the system’s CPU bus – you better get an EE diploma to figure it all out. Or maybe not, as [Linus Åkesson] found out when he created a custom cartridge to boot his Commodordian project from.

For the core of the cartridge a bit of stripboard was sufficient to interface with the C64’s cartridge slot. Despite being single-sided, all the required signals were on one side of the slot. These include the EXROM line that informs the system that a cartridge is present, the ROML line that informs the cartridge when the system is trying to read from it, and of course the data bus. After this the interaction gets somewhat interesting, due to the use of the single-sided stripboard, as the address bus and other signals are on the non-connected side.

Working around this was the biggest challenge, but by creatively using the ROML and DotClk lines and by disabling the display output, the ATmega88 and 74HC541-based cartridge a working solution was created. There is still room for improvement here, naturally, but it would appear that if the goal is simply to autoload software on boot, this is definitely a workable solution. One could also splurge on double-sided stripboard, but that would strip away most of the fun of this solution.