<img src="https://spectrum.ieee.org/media-library/retro-computer-setup-with-text-chips-that-changed-the-world-on-screen.png?id=61658944&width=1245&height=700&coordinates=0%2C341%2C0%2C341"/> Have you ever thought “IEEE Spectrum is terrific, but I just wish I had a way to experience even more of it, perhaps at a local science and technology museum?” Well, I am pleased to say that your very specific wish has been granted! In collaboration with the <a href="https://www.ieee.org/about/history-center" rel="noopener noreferrer" target="_blank">IEEE History Center</a> and the <a href="https://www.ieee.org/about/history-center/globalmuseum" rel="noopener noreferrer" target="_blank">IEEE Global Museum</a> and the support of generous donors, Spectrum’s <a href="https://spectrum.ieee.org/special-reports/chip-hall-of-fame/" target="_self">Chip Hall of Fame</a> has been adapted into a traveling exhibit that has just begun making its way around U.S. museums, and, hopefully, the world.Our Chip Hall of Fame celebrates microchips that have had a significant impact. Six of the chips from the hall were chosen to be part of the “Chips That Shook The World” exhibit, along with artifacts embodying how each was used. One of the chosen was the 8-bit <a href="https://spectrum.ieee.org/chip-hall-of-fame-mos-technology-6502-microprocessor/" target="_self">6502</a> processor, so naturally we thought a <a href="https://spectrum.ieee.org/commodore-64" target="_self">Commodore 64</a> home computer, which used a 6502 variant, should be one of the artifacts. Which led to another thought: Why not have the C64 run a program demonstrating an 8-bit CPU in action?That’s how I ended up, 35 years after I last programmed a C64, sitting at my office desk creating a brand-new plug-in cartridge.The C64 supported <a href="https://www.c64-wiki.com/wiki/Cartridge" rel="noopener noreferrer" target="_blank">plug-in cartridges</a> as a way of distributing software, and our demo program needed to be put on one. Each morning, the museum curator can just turn on the exhibit and presto! The demo program instantly begins running. The alternatives would have required the curator to type in commands to load the demo manually.But this convenience comes with two big caveats: One, the demo has to fit into just 16 kilobytes, the maximum size of a cartridge. Even by the standards of the 1980s, this is small, as some C64 titles spanned <a href="https://www.c64-wiki.com/wiki/Newcomer" rel="noopener noreferrer" target="_blank">hundreds of kilobytes</a> by loading data in chunks from disk or tape. Two, the demo would have to be written in <a href="https://codeburst.io/an-introduction-to-6502-assembly-and-low-level-programming-7c11fa6b9cb9" rel="noopener noreferrer" target="_blank">6502 assembly</a> and control the C64 video hardware directly. <img alt="The components required to make a Commodore 64 cartridge." class="rm-shortcode" data-rm-shortcode-id="167a40e21250b051bf2de61c3854b8d4" data-rm-shortcode-name="rebelmouse-image" id="95d88" loading="lazy" src="https://spectrum.ieee.org/media-library/the-components-required-to-make-a-commodore-64-cartridge.png?id=61614662&width=980"/> Cartridges require 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 mounted in a 3D-printed shell [top left and right]. To make the video output compatible with modern screens, we used a RetroTink-2X Pro adapter [bottom left].James ProvostFortunately, from attending <a href="https://spectrum.ieee.org/theyre-alive-vintage-computer-fans-keep-the-great-machines-of-the-past-running" target="_self">Vintage Computer Federation events</a><a href="https://www.instagram.com/reel/C6ZCubprsSO/" target="_blank"> over the years</a>, I knew there were a lot of free or inexpensive resources that would make it easier than ever before to do this sort of thing.The first step was to figure out just how much I could do in 16 KB. The C64’s graphics hardware was groundbreaking in its day, capable of displaying images of up to 320 by 200 pixels with a palette of 16 colors. It could also display eight sprites at once; each sprite is a moveable single-color 24-by-21 pixel bitmap. The price for this power was complexity. The <a href="https://www.c64-wiki.com/wiki/VIC" target="_blank">video chip’s control registers</a>, screen bitmaps, text-screen data, default and custom character sets, sprites, and color information all live in different locations scattered across memory, with some data actually living in <a href="https://www.c64-wiki.com/wiki/Color_RAM" rel="noopener noreferrer" target="_blank">separate RAM</a> and <a href="https://www.c64-wiki.com/wiki/Character_set" rel="noopener noreferrer" target="_blank">ROM</a> chips.So I sat down with the detailed <a href="https://sta.c64.org/cbm64mem.html" rel="noopener noreferrer" target="_blank">memory maps</a> and <a href="https://www.c64-wiki.com/wiki/Graphics_Modes" rel="noopener noreferrer" target="_blank">video hardware programming guides</a> available for the C64. (This abundance of information is in stark contrast to the 1980s, when documentation was scant, even from Commodore itself). I worked out that I could cram in nine screens of explanatory text, animated graphics, and sprites. Creating these screens, including the custom character sets and sprites they rely on, was greatly simplified thanks to the online C64 graphics editor at <a href="https://petscii.krissz.hu/" rel="noopener noreferrer" target="_blank">petscii.krissz.hu</a>. The editor can output some results as stand-alone assembly programs, which I adapted as subroutines in my demo code.I had just enough space remaining for a lucky find. I wanted to display at least one full-screen bitmapped image, but a prerendered image would have required 8 KB of data, half the cartridge’s capacity. Instead I decided to use a classic hack of programmers since the days of games like<a href="https://en.wikipedia.org/wiki/Rogue_(video_game)" rel="noopener noreferrer" target="_blank"> Rogue</a> and<a href="https://en.wikipedia.org/wiki/Elite_(video_game)" rel="noopener noreferrer" target="_blank"> Elite</a>: pulling free data out of the structure of mathematics by way of <a href="https://en.wikipedia.org/wiki/Procedural_generation" rel="noopener noreferrer" target="_blank">procedural generation</a>.Here’s where I got lucky: I came across the work of Marcello M., who had published the source for a C64 <a href="https://retro64.altervista.org/blog/the-mandelbrot-set-c64-assembly-program-to-draw-it-fast-using-integer-math-part-1/" rel="noopener noreferrer" target="_blank">assembly program</a> that quickly created a multicolor fractal <a href="https://en.wikipedia.org/wiki/Mandelbrot_set" rel="noopener noreferrer" target="_blank">Mandelbrot set</a> using just 3.3 KB of code. With Marcello’s blessing, I incorporated his code as another subroutine.<h2>Modern Tools For Writing C64 Software</h2>The coding was done using the free <a href="https://sites.google.com/view/ide65xx" rel="noopener noreferrer" target="_blank">IDE 65xx</a> and <a href="https://theweb.dk/KickAssembler/Main.html" rel="noopener noreferrer" target="_blank">Kick Assembler</a> desktop software. I was able to test the code using the popular C64 <a href="https://vice-emu.sourceforge.io/" rel="noopener noreferrer" target="_blank">Vice emulator</a>, which allowed me to do handy things like examining live memory contents to find runtime bugs. <img alt="A diagram showing 64 kilobytes of RAM with a Kernal ROM occupying the top 8 KB, followed by 4 KB of character ROM, and then 8 KB of Basic ROM. Another column shows I/O and color RAM mapped to the same position as the character ROM, and two shadow ROM locations in lower memory. Finally a third column shows a 16 KB cartridge ROM overlapping the Basic ROM and the memory below it." class="rm-shortcode" data-rm-shortcode-id="2a6b3df1e313beface7174cd6588630c" data-rm-shortcode-name="rebelmouse-image" id="71b5d" loading="lazy" src="https://spectrum.ieee.org/media-library/a-diagram-showing-64-kilobytes-of-ram-with-a-kernal-rom-occupying-the-top-8-kb-followed-by-4-kb-of-character-rom-and-then-8-kb.png?id=61613059&width=980"/> Regions of the Commodore 64’s RAM were mapped to things like the system ROMs, video-color memory, and the bitmaps of characters, the latter of which were actually mapped to multiple locations in RAM when accessed by the video hardware. Some of these mappings overlapped: Inserting a 16-KB cartridge automatically disabled the ROM storing the Basic interpreter. James ProvostThe next step was to make a physical cartridge. Again, there’s modern help, this time in the form of US $5 printed circuit boards that need just a handful of components soldered in to make a cartridge. These components include a programmable ROM chip that I picked up for <a href="https://www.ebay.com/itm/363498306025" target="_blank">$3 on eBay</a>. I burned my code to the memory chip with my trusty <a href="http://autoelectric.cn/EN/TL866_main.html" target="_blank">TL866 programmer</a> and mounted it to the PCB, which in turn was mounted into a <a href="https://www.thingiverse.com/thing:692797" target="_blank">3D-printed cartridge case</a>.Then came the moment of truth. It probably won’t come as a surprise to regular readers that I already own an original C64, which I connect to modern flat-screen displays via a <a href="https://www.retrotink.com/shop/retrotink-2x-pro" target="_blank">RetroTink-2X Pro</a> adapter. So I carefully pushed the cartridge into its slot and turned the machine on.Naturally, my C64 immediately froze up. I had forgotten to remove a little bit of memory-management code that made the demo work in the Vice emulator by disabling the ROM that stores the C64’s Basic interpreter. On the real hardware, this snippet ended up disabling half the cartridge’s memory. A quick edit and a trip back to the TL866 and I was ready to try again. Success! I was finally literally ready to ship some software, all the way to <a href="https://www.uplandexhibits.com/" target="_blank">Upland Exhibits</a>, the people building our traveling display.I hope you get a chance to see my little demo and our “Chips That Changed The World” exhibit in person: We’ll post current and upcoming locations on the Chip Hall of Fame page. But in the meantime, whether you used the C64 back in the day, or are just looking for a fun coding challenge, I recommend trying your hand at programming this 8-bit classic, now that so many of the original pain points have been reduced!

أخبار مثيرة لعشاق الحوسبة القديمة! تعاونت IEEE Spectrum مع المتاحف المحلية للعلوم والتكنولوجيا لتقديم فرصة فريدة لبناء وحدة تخزين Commodore 64 الخاصة بك. لا تتيح هذه المبادرة للمعجبين فقط استعادة ذكريات الألعاب الكلاسيكية، بل تعزز أيضًا التعلم العملي والانخراط مع التكنولوجيا. إنها طريقة رائعة للتواصل مع الماضي بينما تلهم الأجيال القادمة في مجال الحوسبة.

¡Noticias emocionantes para los entusiastas de la computación retro! IEEE Spectrum se ha asociado con museos locales de ciencia y tecnología para ofrecer una oportunidad única de construir tu propia cartucho de Commodore 64. Esta iniciativa no solo permite a los fanáticos revivir la nostalgia de los juegos clásicos, sino que también promueve el aprendizaje práctico y el compromiso con la tecnología. Es una forma fantástica de conectar con el pasado mientras se inspira a las futuras generaciones en el campo de la computación.

Une nouvelle passionnante pour les amateurs d'informatique rétro ! IEEE Spectrum s'est associé à des musées locaux de science et de technologie pour offrir une occasion unique de construire votre propre cartouche Commodore 64. Cette initiative permet non seulement aux fans de revivre la nostalgie des jeux classiques, mais elle favorise également l'apprentissage pratique et l'engagement avec la technologie. C'est une excellente façon de se connecter au passé tout en inspirant les générations futures dans le domaine de l'informatique.

Exciting news for retro computing enthusiasts! IEEE Spectrum has teamed up with local science and technology museums to offer a unique opportunity to build your own Commodore 64 cartridge. This initiative not only allows fans to relive the nostalgia of classic gaming but also promotes hands-on learning and engagement with technology. It's a fantastic way to connect with the past while inspiring future generations in the field of computing.