The Commodore 64 (C64) holds a particular place within the historical past of private computing. Launched in 1982 by Commodore Worldwide, it rapidly grew to become an iconic machine and an emblem of the house laptop revolution. The recognition of the Commodore 64 was unparalleled, and even to at the present time, it stays the best-selling laptop mannequin of all time. Its affordability, versatility, and in depth software program library made it a beloved selection for each gaming and productiveness.
Throughout its prime, the Commodore 64 was a game-changer on the earth of computing. Priced competitively at $595, it was accessible to a variety of customers. Its superior graphics and sound capabilities, particularly for its time, made it a dominant drive within the gaming business. Numerous classics, reminiscent of “Maniac Mansion,” “Pitfall,” and “Summer season Video games,” had been developed for the C64, charming a complete era of avid gamers.
At this time, the Commodore 64 continues to be cherished by a devoted neighborhood of fans and collectors. Its legacy lives on via numerous emulators, {hardware} remakes, and preservation efforts. The retro computing scene thrives with people who tinker, modify, and develop new software program and {hardware} for the C64. Quite a few on-line communities nonetheless present platforms for sharing information, discussing initiatives, and reliving the nostalgia related to this iconic machine.
The growth port can be utilized for cartridges (📷: Linus Åkesson)
Linus Åkesson is most undoubtedly counted among the many modern-day followers of the Commodore 64. In reality, he loves this traditional laptop a lot that he spent over three years constructing what he calls the Commodordion — a playable accordion made out of a pair of Commodore computer systems and a stack of floppy disks. If that isn’t love, we don’t know what’s!
Whereas the Commodordion is magnificent, even when not particularly helpful, it does have one notable disadvantage. The software program that powers the pc is loaded from a cassette tape drive emulator. It really works, positive, however it’s gradual and entails some handbook steps to get it up and operating, to not point out that cassette tape-based storage is notoriously unreliable.
Due to his familiarity with the pc, Åkesson knew {that a} customized cartridge would clear up the issue. They’re quick, dependable, and don’t require any handbook steps besides. However to interface with the growth port, a customized PCB is required. Positive, it’s cheap to have a customized PCB produced nowadays, however it usually takes a number of weeks to get one in your palms. So Åkesson thought-about extra DIY-friendly choices he may construct with components he already had readily available.
A stripboard appeared like a pure choice, and the 0.1″ spacing between pads even matched up with the pinout of the Commodore’s growth port. However there was one huge drawback with this concept — the stripboard solely has contacts on one aspect, however the growth port has contacts on either side. Undeterred, Åkesson studied the pinout of the growth port, and realized that he may be capable of get by utilizing solely the pins on the highest aspect of the connector.
The finished customized cartridge (📷: Linus Åkesson)
At first look, this would appear not possible as a result of the deal with pins are on the underside portion of the connector. How can the pc ask for information from particular reminiscence addresses with out specifying the deal with, in any case? Åkesson realized that, as long as information is being accessed sequentially, you do not want to know every deal with. You’ll be able to merely current one byte after the opposite on the information bus as they’re requested. However how have you learnt when they’re being requested? Simple sufficient, simply watch the chip choose line for the ROM chip — when it goes low, put the subsequent byte on the bus.
Within the spirit of working with what he had readily available, an ATmega88 microcontroller was utilized to service the pc’s requests, at the side of a tristate buffer to take away it from the information bus when information was not being requested. This microcontroller has 8 KB of flash reminiscence, which is enough for the Commodordion’s wants anyway, however it isn’t rather a lot, even for a Nineteen Eighties laptop. So, the out there reminiscence had for use correctly, with this system being tightly packed in.
The answer for this drawback was to incorporate a small bootloader that writes itself to the pc’s RAM. This bootloader then sequentially grabs program information from the customized cartridge to load into system reminiscence. Utilizing this DIY cartridge, the Commodordion can boot up immediately after powering up.
Åkesson has produced a really detailed write-up with step-by-step directions for anybody that want to reproduce the work. In case you are not desirous about accordions, how a few theremin? Or possibly you want to do some machine studying along with your Commodore?