commodore 64

135 Articles

A hand holding a One ROM with a Commodore 64 in the background

One ROM: The Latest Incarnation Of The Software Defined ROM

September 3, 2025 by 25 Comments

Retrocomputers need ROMs, but they’re just so read only. Enter the latest incarnation of [Piers]’s One ROM to rule them all, now built with a RP2350, because the newest version is 5V capable. This can replace the failing ROMs in your old Commodore gear with this sweet design on a two-layer PCB, using a cheap microcontroller.

[Piers] wanted to use the RP2350 from the beginning but there simply wasn’t space on the board for the 23 level shifters which would have been required. But now that the A4 stepping adds 5 V tolerance [Piers] has been able to reformulate his design.

The C64 in the demo has three different ROMs: the basic ROM, kernel ROM, and character ROM. A single One ROM can emulate all three. The firmware is performance critical, it needs to convert requests on the address pins to results on the data bus just as fast as it can and [Piers] employs a number of tricks to meet these requirements.

The PCB layout for the RP2350 required extensive changes from the larger STM32 in the previous version. Because the RP2350 uses large power and ground pads underneath the IC this area, which was originally used to drop vias to the other side of the board, was no longer available for signal routing. And of course [Piers] is constrained by the size of the board needing to fit in the original form factor used by the C64.

The One ROM code is available over on GitHub, and the accompanying video from [Piers] is an interesting look into the design process and how tradeoffs and compromises and hacks are made in order to meet functional requirements.

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Commodore Is Back Selling New C64s, But Should You Buy Them?

August 17, 2025 by 107 Comments

It’s hard to argue with nostalgia, but you can toss a bucket of cold facts over it. In the case of the recent rescuing of the Commodore brand from the clutches of relabeling of generic electronics by [Perifractic] of Retro Recipes, we got [The Retro Shack] doing the proverbial bucket dumping in a new video. Basically the question is whether the fresh Commodore 64 offerings by the new-and-improved Commodore are what you really want, or need.

The thing is that over the decades many people have created all the bits that you need to build your own classical C64, or even buy one off-the-shelf, with people like [bwack] having reverse-engineered the various C64 mainboards. These can be populated with drop-in replacements for chips like the SID, VIC-II, CIAs and others that are readily available, along with replica cases and keyboards. If you crave something less bulky and complex, you can run a bare metal C64 emulator like BMC64 on a Raspberry Pi, or just run the VICE emulator on your platform of choice. There’re also options like the full-sized TheC64 and Ultimate 64 Elite II systems that you can buy ready to go.

Basically, there is a whole gamut of ways to get some part of the C64 experience, ranging from emulator-only to a full hardware DIY or pre-assembled format. Each of which come with their own price tag, starting at $0 for running VICE on your existing system. With so much choice we can only hope that the renewed Commodore company will become something more than Yet Another C64 Experience.

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Repairing An Obscure Apple II Clone

August 3, 2025 by 8 Comments

The Apple II was made in great numbers, as was the Commodore 64. But the Mimic Spartan? It was a weird Apple II clone that you needed a Commodore 64 to use. [ARC Javmaster] has found one of these obscure machines and has set about bringing it back to life. Check out the video below.

The story of the machine has been told online by one of the developers on the project, one [Brent Marykuca]. Basically, the Mimic Spartan was an Apple II clone that was intended to take advantage of a C64 as a host machine. It came in a beige box with a bunch of edge connectors and cables sticking out, and you were intended to nest it on the back of your C64 so it could hook up to all the ports. Then, you could use your machine as a C64 or an Apple II, or sort of… both… and even exchange data between both machines in some limited ways. There are also a few details of this obscure machine that have been collated by [Mike Naberezny], who is seeking the original disk that shipped with the machine when new.

It’s early days yet for [ARC Javmaster]’s efforts to restore the Mimic Spartan. Thus far, it’s had a clean and basic test. It was able to display a short line of text on a display before ceasing activity. A full boot hasn’t been achieved just yet, but we can’t wait to see where the resurrection efforts go next.

Back in the day, there were all kinds of Frankenstein computer cards that effectively put one kind of computer inside another. These days, you can condense an entire retro machine down to run on a single microcontroller.

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Commodore 64 On New FPGA

July 28, 2025 by 19 Comments

When it comes to getting retro hardware running again, there are many approaches. On one hand, the easiest path could be to emulate the hardware on something modern, using nothing but software to bring it back to life. On the other, many prefer to restore the original hardware itself and make sure everything is exactly as it was when it was new. A middle way exists, though, thanks to the widespread adoption of FPGAs which allow for programmable hardware emulation and [Jo] has come up with a new implementation of the Commodore 64 by taking this path.

The project is called the VIC64-T9K and is meant as a proof-of-concept that can run the Commodore 64’s VIC-II video chip alongside a 6502 CPU on the inexpensive Tang Nano 9k FPGA. Taking inspiration from the C64_MiSTer project, another FPGA implementation of the C64 based on the DE10-Nano FPGA, it doesn’t implement everything an original Commodore system would have had, but it does provide most of the core hardware needed to run a system. The project supports HDMI video with a custom kernel, and [Jo] has used it to get a few demos running including sprite animations.

Built with a mix of Verilog and VHDL, it was designed as a learning tool for [Jo] to experiment with the retro hardware, and also brings a more affordable FPGA board to the table for Commodore enthusiasts. If you’re in the market for something with more of the original look and feel of the Commodore 64, though, this project uses the original case and keyboard while still using an FPGA recreation for the core of the computer.

a Coleco Adams console on a desk

Coleco Adam: A Commodore 64 Competitor, Almost

July 21, 2025 by 67 Comments

For a brief, buzzing moment in 1983, the Coleco Adam looked like it might out-64 the Commodore 64. Announced with lots of ambition, this 8-bit marvel promised a complete computing package: a keyboard, digital storage, printer, and all for under $600. An important fact was that it could morph your ColecoVision into a full-fledged CP/M-compatible computer. So far this sounds like a hacker’s dream: modular, upgradeable, and… misunderstood.

The reality was glorious chaos. The Adam used a daisy-wheel printer as a power supply (yes, really), cassettes that demagnetized themselves, and a launch delayed into oblivion. Yet beneath the comedy of errors lurked something quite tempting: a Z80-based system with MSX-like architecture and just enough off-the-shelf parts to make clone fantasies plausible. Developers could have ported MSX software in weeks. Had Coleco shipped stable units on time, the Adam might well have eaten the C64’s lunch – while inspiring a new class of hybrid machines.

Instead, it became a collector’s oddball. But for the rest of us, it is a retro relic that invites us to ponder – or even start building: what if modular computing had gone mainstream in 1983?

Let’s Buy Commodore! Well, Somebody Is.

June 7, 2025 by 62 Comments

When a man wearing an Atari T-shirt tells you he’s buying Commodore it sounds like the plot for an improbable 1980s movie in which Nolan Bushnell and Jack Tramiel do battle before a neon synthwave sunset to a pulsating chiptune soundtrack. But here on the screen there’s that guy doing just that, It’s [Retro Recipes], and in the video below he’s assembling a licensing deal for the Commodore brand portfolio from the distant descendant of the Commodore of old.

It’s a fascinating story and we commend him for tracing a path through the mess that unfolded for Commodore in the 1990s. We tried the same research path with a friend a few years ago and ended up with an anonymous Dutch paper company that wouldn’t answer our calls, so we’re impressed. In conjunction with several other players in the Commodore retrocomputing world he’s trying to assemble a favourable percentage deal for manufacturers of new parts, computers, and other goodies, and we’re pleased to see that it’s for the smaller player as much as for the industry giant.

When looking at a story like this though, it’s important not to let your view become clouded by those rose tinted glasses. While it’s great that we’re likely to see a bunch of new Commodore-branded Commodore 64s and parts, there are many pitfalls in taking it beyond that. We’ve seen the Commodore logo on too many regrettable licensed products in the past, and we fear it might be too tempting for it to end up on yet another disappointing all-in-one video game or just another budget PC. If something new comes out under the Commodore brand we’d like it to be really special, exploiting new ground in the way the Amiga did back in the day. We can hope, because the alternative has dragged other famous brands through the mud in recent years.

If you want an insight into the roots of the original Commodore’s demise, have a read of our Hackaday colleague [Bil Herd]’s autobiography.

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The Commodore 64 Gets An HDMI Upgrade

May 25, 2025 by 39 Comments

The Commodore 64 may remain the best selling computer of all time, but it has one major flaw. It doesn’t have HDMI! That makes it a total pain to use with modern displays. Thankfully, [Side Projects Lab] has whipped up an HDMI output board to solve this concerning oversight from the original designers.

The project was inspired by work by [Copper Dragon], who whipped up a nifty RGB output board. This device worked by reading the inputs to the C64’s VIC II graphics chip, which it then used to recreate a pixel-perfect video frames to then produce a quality analog video output. [Side Projects Lab] figured the same interception technique would be useful for producing a quality HDMI output.

The result was the HD-64. It sits inside the C64 in place of the original RF modulator. It uses an interleaver socket to capture digital signals going to the VIC II. It then feeds these signals to an emulated VIC II running inside an FPGA, which creates the pixel-perfect screen representation and synthesizes the proper digital HDMI output. Meanwhile, the analog audio output from the SID chip is captured from the RF modulator’s original header, and sent out via the HDMI output as well. The default output is super-sharp, but the device can be configured to allow scanlines and anti-aliasing if that’s more to your tastes.

If you want to hook your C64 up to a modern screen, this is going to be one of the tidiest and sharpest ways to do it. We’ve seen similar hacks for other platforms before, too. Video after the break.

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