Some Assembly Required
Between 1992 and 1995, I reverse engineered Commodore 64 applications by printing their disassemblies on paper and adding handwritten comments (in German). These are the PDF scans of the 62 applications, which are 552 pages total.
The text screen of the Commodore 64 has a resolution of 40 by 25 characters, based on the hardware text mode of the VIC-II video chip. This is a step up from the VIC-20’s 22 characters per line, but since computers in the professional segment (Commodore PET 8000 series, CP/M, MS-DOS) usually had 80 columns, several solutions – both hardware and software – exist to allow 80 columns on a C64 as well. Let’s look at how this is done in software! At the end of this article, I present a fast and full-featured open source implementation with several different character sets.
Many reverse-engineered versions of “KERNAL”, the C64’s ROM operating system exist, and some of them even in a form that can be built into the original binary. But how about building the original C64 KERNAL source with the original tools?
The GEOS operating system managed to clone the Macintosh GUI on the Commodore 64, a computer with an 8 bit CPU and 64 KB of RAM. Based on Maciej Witkowiak's work, I created a reverse-engineered source version of the C64 GEOS 2.0 KERNAL for the cc65 compiler suite:
Major GEOS applications on the Commodore 64 protect themselves from unauthorized duplication by keying themselves to the operating system's serial number. To avoid tampering with this mechanism, the system contains some elaborate traps, which will be discussed in this article.
If you have developed applications for the Commodore 64 in the 80s or 90s, chances are you still have your old floppy disk with the original assembly sources. If you have used the VisAss or
F8 AssBlaster assemblers, you can use a new command line tool I wrote to convert the encoded binary files into ASCII, so they can be published or you can continue development using modern tools like cc65.
The Final Cartridge III was one of the major multi-function extension cartridges for the Commodore 64. It contained BASIC extensions, floppy and tape speeders, centronics printer support, screen editor extensions including F-key shortcuts, a monitor, a freezer – and a GEOS-like windowing system called “Desktop”. In all this, the FC3 integrated seamlessly with the look-and-feel of the stock Commodore 64: It did not change anything (same screen colors and banner!), it only extended functionality in consistent ways.
“The Wave” is a Web Browser for GEOS (with the Wheels extension) on C64/C128 machines with a SuperCPU and a RAM extension.
geowrite2rtf is a tool that converts Commodore 64/128 GEOS GeoWrite documents into RTF format. Most formatting will be preserved, but some formatting and graphics will be discarded.
The Commodore 64 ROM has been subject to immense reverse engineering. Many commented disassemblies were published over the decades, scattered over different media such as books, magazines, disks, and later, the internet – and there are even some commentaries that apply to the C64 ROM, but were written with other systems in mind that shared Microsoft’s BASIC interpreter.
On my quest of collecting as many commentaries on the Commodore 64 ROM at pagetable.com/c64rom, we have gathered Lee Davison’s excellent commentary, the German de facto standard by Data Becker, and an adaptation of Bob Sander-Cederlof’s Apple II ROM commentary, all in the same cross-referenced HTML format.
In our series about C64 ROM commentaries (English version by Lee Davison, German version by Data Becker), I’m now presenting a most unusual C64 ROM commentary – based on a commented disassembly of the Apple II ROM.
After last week’s German C64 ROM disassembly from the “64 intern” book, I have now also converted Lee Davison’s commented disassembly into the same format.
Whenever I need to look up some code in the ROM of the Commodore 64, I have the choice of the commented disassembly by Marko Mäkelä, the one by Ninja/The Dreams, or the one by Lee Davison – or I can just use my paper copy of “Das neue Commodore-64-intern-Buch“, an excellent line-by-line commentary in German.
by Mike Pall, published with permission.
(This article is about a German-language podcast episode on the C64.)
Update: The source is available at github.com/mist64/fastboot1541
Nobody doubts that the C64 was the greatest selling single computer model of all time, it even made it into the Guinness Book of World Records, but nobody quite knows how many it really was: Most sources say 17 million, others say 22 or even 30 million. With a high degree of confidence, I can now say that Commodore only sold 12.5 million units – how I would know that, you ask, and how do I dare to contradict well-known facts? By analyzing serial numbers!
The “Final Cartridge III” has been among the most popular Commodore 64 extensions, providing a floppy speeder, BASIC extensions, a machine language monior, a freezer and even a (rarely used) graphical desktop. The major advantage compared to other C64 cartridges is the consistent way in which the Final Cartridge III extends the C64 experience.
Download the Apple Keynote 08 presentation.