Create your own commodore 64 cartridge

Have you ever thought “IEEE The spectrum is very good, but I want me to have a way to experience it, perhaps in a local science and technology museum? “Well, I am happy to say that you have been given a very special wish!” IEEE History Center And this IEEE Global Museum And support of liberal donors, SpectrumThe Chip Hall of Fame has been adapted to a travel performance, which has just started making its way around our museums, and, hope that the world.

Our Chip Hall of Fame Celebrates Microchips which has a significant impact. The six chips of the hall were chosen to be part of the “chips that shook the world”, as well as how each was used along with artifacts. One of the chosen 8-bit was 6502 processor, so naturally we thought that a commodore 64 home computer, which uses the 6502 version, must be one of the artworks. Due to which another idea was: Why not C64 has run a program that performs 8-bit CPU in action?

In this way I ended, after 35 years when I last programmed the C64, my office made a brand-new plug-in cartridge sitting at the desk.

C64 supported Plug-in cartridge As a way to distribute software, and our demo program needs to be put on one. Each morning, the museum curator can only turn on exhibitions and presesto! The demo program starts running immediately. The alternative will require the curator to type the command to manually load the demo.

But this feature comes with two large cavets: one, the demo has to fit only 16 kilobite, the maximum size of a cartridge. Even according to the standards of the 1980s, it is small, as some C64 titles have been spanned. Hundreds of kilobite By loading the data from discs or tapes. Two, you have to be written in the demo 6502 Assembly And control the C64 video hardware directly.

The cartridge requires only a few components: a printed circuit board (bottom right), programmable memory chip (bottom middle), and some resistors, diodes, and a capacitor (top middle). They are placed in a 3D-print shell (top left and right). To make the video output compatible with the modern screen, we used a retrotink -2 x Pro adapter (bottom left).James provost

Luckily, by participating in vintage computer federation events Over the yearsI knew that there were lots of free or cheap resources that would make such work more easier than ever.

The first step was to find out how much I can do in 16 KB. The graphics hardware of C64 was doing groundbreaking on its day, able to display images up to 320 by 200 pixels with 16 colors palettes. It can also display eight sprites at a time; Each spright is a moving single-color 24-by-21 pixel bitmap. The price of this power was complexity. Video chip control registerScreen bitmaps, text-screen data, default and custom character sets, sprites, and color information all live in various places scattered in memory, some data really live. Different Ram And Rom Chips.

So I sat with the wide Memory map And Video hardware programming guide C64 available for. (This abundance of information is unlike the 1980s, when the documentation was a scent, even from the Comodore). I worked that I can rote in nine screens of explanatory text, animated graphics and sprites. Creating these screens, including custom character sets and sprights they rely, was very simple thanks to the online C64 graphics editor. petscii.krissz.huThe editor can output certain results as a stand-alone assembly program, which I have adapted as subrutin in my demo code.

I just had enough space remaining for a lucky search. I wanted to display at least one full-screen bitmapped image, but an predecessor image would require 8 KB data, half cartridge ability. Instead I decided to use a classic hack of the programmer from the days of the game. Wicked And Aristocrat class: Data free from the composition of mathematics through Procedural production,

Here I am lucky: I came in the work of Marcello M, who published the source for C64 Assembly program It quickly made a multicolor fractal Mandelbot set Using just 3.3 KB code. With the blessings of Marcello, I included their code as another subrutin.

Modern equipment for writing c64 software

Coding was done using free Ide 65xx And Kick assembler Desktop Software. I was able to test the code using the popular C64 Vice emulatorWhich allowed me to do easy things like checking live memory material to find a runtime bug.

The areas of RAM of Commodore 64 were mapped for things such as Systems Rome, Video-Family Memory, and Betamap of the characters, of which were later mapped in many places in the RAM when the video was accessed by the video hardware. Some of these mapping overlaps: Inserting a 16-KB cartridge, automatically disables the ROM that stores the original interpreter. James provost

The next step was to make a physical cartridge. Again, there is modern help, this time as US $ 5 printed circuit boards, which require just a handful of components to make cartridges. These components include a program worthy Rome chip that I had picked up $ 3 on ebayI burnt my code in memory chip with my trustee TL866 programmer And mounted it in PCB, which was mounted in one in return 3D-crushed cartridge case,

Then the moment of truth came. This will probably not come as a surprise for regular readers that I am already the owner of an original C64, which I connect with a modern flat-screen display through one Retrotink -2 x Pro Adapter. So I carefully pushed the cartridge into its slot and turned on the machine.

Naturally, my C64 immediately froze. I forgot to remove a small portion of the memory-maneuch code that worked in the vice emulator by disabled ROM, which stored the original interpreter of C64. On real hardware, this snipet disabled half of the cartridge. A quick editing and a trip back on TL866 and I was ready to try again. Success! I was finally ready to ship some software, in all ways Upland performsPeople who produce our travel performance.

I hope you will get a chance to see my small demo and our “Chips the New World” performance: We will post the current and upcoming places on the Chip Hall of Fame page. But in the meantime, whether you have used C64 a day, or just looking for a fun coding challenge, I advise this 8-bit classic to try my hand in programming, now so many basic pain points have reduced!