Written and Maintained by Gregory Nacu

C64 OS has one goal.
Make a Commodore 64 feel fast and useful in today’s modern world.

It's a very high bar. The C64 was introduced in 1982 and has an 8-bit, 1MHZ, 6510 CPU with just 64 kilobytes of directly addressable memory. It has a screen resolution of 320x200 pixels, and a fixed palette of 16 colors. But, it is an incredibly versatile machine. And it enjoys an active userbase and a great variety of modern hardware expansions.

The C64 has had many operating systems written for it, 1 So why write another?

Some of these projects were designed to be experimental, or to demonstrate a point, rather than to solve a problem or to make using the C64 better. Others had good intentions but pushed the machine in ways it wasn't designed for, compromising on speed and usability in the pursuit of features available on more powerful computers. The aim of C64 OS is to work with the limitations of the Commodore 64 and enable it to become useful.

  1. In alphabetical order: CLiPS, Contiki, GeckOS/A65, GEOS, LUnix/LNG, Wheels, WiNGs. And I'm sure more. []

Author History

Smiling face of Gregory Nacu, the author and maintainer of C64os.com

Gregory Nacu
Author and maintainer of C64OS.com
See nacu.ca for a full bio

I've been a Commodore 8-bit user since I discovered my first computer, a broken Vic-20, under the bed in my parents' guest room when I was 5 years old. They had it repaired for $40 and my journey into computing began.

When I was 9 years old, I got my first Commodore 64 for Christmas in 1990. It changed my life. During the mid 90s I discovered Creative Micro Designs and started buying as much hardware as I could afford. I ended up with numerous C64's C64c's, c128's, a couple of Vic-20's, a c128D and an SX-64. I also got a SuperCPU64 and SuperCPU128 both maxed out with 16megs of SuperRam. I got a Turbo232 and a 33.6Kbps modem and started surfing the web via a dialup shell account. My collection of great hardware kept growing to include a smartmouse, a RamLink, a CMD HD and a SID Symphony. I also acquired numerous Commodore disk drives, 1541's, 1541 II's, 1571's and a 1581.

I started to attend Commodore Expos in the United States in 1998 when I was 17 years old. I showed up with a C64 breadbin slung over my back on a guitar strap. I was in heaven. There were so many cool people and so much great activity going on. I started to dabble more seriously into programming in the late 90s. Shortly thereafter I got hold of an IDE64, and discovered that Jolz Maginnis from Australia was working on a preemptively multi–tasking Unix–like OS for the SuperCPU64, WiNGs (née JOS). I worked with him over IRC to help him debug the TCP/IP stack and my life changed again.

With his tremendous help I taught myself to program in C, and began cross compiling WiNGs software on an iMac and FTPing it to my 64. I cut my teeth writing a bunch of software I had only ever dreamed of having on my C64 when I was kid. And I began to give presentations at Commodore Expos showing off such creations as a Movie player and SpiffyPaint, a multi–layer drawing program. It was a fun and glorious time of my life that I'll never forget.

Present Day

Eventually CMD shut its doors, and the SuperCPU sadly became unavailable. We all grew up, got jobs and moved on with our lives. I packed up my equipment when I moved houses and I didn't have the time to pull it back out. I got married, moved again, and now I've got two children.

When I came back to the scene after 8 years away, I found a bustling community, full of life and energy, with many new projects to fill in the gaps where CMD had left off. A high speed RS232 adaptor and a 56K modem are no longer relevant to today's world. But now we have multiple ethernet adaptors, commercially available. The CMD HD, and RamLink seem woefully ancient, with bulky SCSI spinning harddisks, or 30 pin RAM simms. Instead SD card adaptors are now commercially available in sizes that make them much more useable. Plus they make exchanging data with a PC/Mac easier and faster than it ever was in the heyday.

The SuperCPU is not available. But there are lots of C64s and they need our love. So I have forced myself to get used to the feeling and the pace of 1Mhz again. It was hard to go back from 20Mhz, and even harder to go back from 2.5Ghz. But you do get used to it. What the C64 lacks right now, is a platform upon which to write network–based applications. That's what I want to write, but there is very little out there to help me do that. So, instead, I'm writing a simple single–tasking OS, that will provide the essentials to make it easier to write the apps I've got a creative itch to work on; network–oriented with a consistent mouse–based UI.

This site is about my work on C64 OS, but it's also about helping new and returning users get informed about what is out there, so that you too can live and love your Commodore 64.

I've spent and will continue to spend hundreds of hours working on C64 OS, the Buyer's Guide and the other content of this site. If you want to support my work and help make these projects a reality, please consider sending me a donation via PayPal. Thank you for your support!


C64OS.com has grown from its original purpose as an outlet for me to blog about my adventures in learning to code in 6502 and my progress towards the development of a simple, single–tasking, event–driven operating system. It is growing into a resource for new and returning users of the Commodore 64 and 128 to find out about all the great new things being developed both in hardware and software.

Below you'll find links to the main sections of this site: C64 OS: Technical Documentation, C64 Luggable: Project Overview, the C64 OS development progress weblog, and a Buyer's Guide to commercially available C64 compatible hardware products, projects and kits.

C64 OS: Technical Documentation


The site is named for this main and overarching project, C64 OS, which I began developing in the fall of 2016. Its goal is to be simple and to work with the hardware limitations to make a truly authentic C64 OS, rather than trying to ape the behaviour of other OS platforms. It exists to provide usability advantages for the user, and development advantages for the programmer.


  • Event–driven execution model
  • Multi–layer text screen compositor
  • Advanced mouse and keyboard event system
  • Hybrid memory manager
  • PETSCII/ASCII conversion
  • Full-screen, menu based UI
  • Nested Widget Toolkit
  • Standardized open and save file dialogs
  • Efficient string and text management
  • Universal cut, copy and paste
  • Application launcher

C64 OS is under active development, and has not yet undergone an initial beta release.

C64 Luggable: Project Overview

In 2000 I acquired my first SX-64 Executive Computer. A luggable C64 with a built in 5" display, 1541 floppy drive and a unified power supply. All with a handle on the top. I heavily modified mine to include a SuperCPU, IDE64, CD-Rom drive, Ethernet adaptor and High Speed RS232, all powered of a lightweight AT Power Supply.

But the SX-64 was built for a different time. Its display is a massive CRT block, 1' deep. The rest of the internal layout is modeled around this main feature. C64 Luggable is a project to build an all–in–one C64, oriented vertically rather than horizontally. It has a large 15" LCD display and foregoes old tech like a floppy drive, in favor of SD card based storage. And ethernet will be a standard.

I love my Commodore computers and how expandable they are, but they have a tendency to take up a whole desk with sprawling peripherals and multiple power supplies. This makes them inconvenient to take with you. C64 Luggable is a practical project for me, and a reference design for other people to be creatively inspired. It will allow me to bring a C64 with me to my friends' houses, to remove the friction of getting them to be able to enjoy C64 demos and multi–player games with me.

Weblog: C64 OS Development Progress Weblog

This site begans its life as a simple blog where I could write about learning 6502 programming and the low–level workings of the C64, while I develop C64 OS.

I am an amateur author, however, and I didn't want to constrain my writing to just technical information. So I began writing editorials about Commodore–related hardware, magazines, events and more. The problem was that these nuggets became hard to find as they fell below the surface due to the addition of new posts.

The site changes provide explicit places write technical documentation for C64 OS, an overview of the C64 Luggable project and a Buyer's Guide to commercially available Commodore compatible expansion hardware. This frees the blog from carrying the burden of all of the whole site. There is now much more room on the blog's own page. Its sidebar now has the freedom to index the most recent posts, showcase featured posts and makes the blog itself easier to navigate.

I have been fairly consistent about making one post per week. That feels like a maintainable pace for me. But it can be difficult to get regular readers if new content is not showing up more frequently. To help cope with this, the weblog also has an RSS feed. Subscribe to it, and you'll get new articles in your feed reader the as soon as they are published.

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Recent Posts

October 18, 2017Programming Theory

A C64 OS App's Start Of Life

September 26, 2017Hardware

New C64c Cases Available

September 18, 2017Programming Theory

Organizing a Big Module

Buyer's Guide: Product, Project and Kit Catalog

Commodore hardware is great. The architecture has proven to be very well designed as it is still usable and expandable over 30 years later. Part of what makes the system so great is how easily it can be expanded. But in order to take advantage of that design architecture, you need to actually expand it by building or purchasing expansion hardware.

Commodore 8-bit computers have had lots of third–party supporting hardware. And while much of it is no longer available, there are many modern projects and expansion options that are available and under development today. When I returned from my hiatus, I was amazed by the rich support from hardware and software and even publications. However, I learned about these things in dribs and drabs by haunting IRC channels, message boards and following C64 fans on Twitter.

The Buyer's Guide is an online catalog of all the hardware products, projects and kits that are commercially available today. Including photos, links to supporting software, reviews, and prices and links to where you can buy these for yourself. The guide also includes some features on hardware that was not specifically designed for Commodore Computers, but which are incidentally compatible and may be of great value in building a killer Commodore rig.