Konstantin Dimitrov Fires Up the Base-18, World's First General-Purpose PIC18 Microcomputer

Konstantin Dimitrov has published a video showcasing his 'retro' computer platform with a difference: It's based on the Microchip PIC18, rather than a truly vintage processor or the popular AVR8 — because, he explains, "there won’t be any educational benefit to anyone in a system that uses architecture which has not been mainstream for many years already."

Dubbed the Base-18, Dimitrov's prototype started as a desire to make a custom eight-bit computer. Having discarded "old-school" processors choices used to power the eight-bit micros of the 1970s and onwards, Dimitrov made an unusual choice. "I then went through all other current 8-bit platforms and in the end narrowed the choice down to two options – PIC18 or AVR8," he states. "The latter is arguably the best 8-bit architecture every created and presents a really attractive option. I however decided to build the computer around PIC18 because no one has ever made a decent open and expandable system around it, and it also offers more fun in the process."

Having picked the PIC18F87K22 to power the system, Dimitrov turned to architecture — and settled on an interesting hybrid design which combines an ability to run as a standalone single-board computer while offering an Altair-style system bus to which additional boards can be connected. "My inspiration and benchmark for this system came both from the excellent RC2014 computer, and the 'master of them all' – the original IBM PC," Dimitrov says, "however I put a slightly different goal ahead with an attempt to create a true 21st century 8-bit system that appeals not only to the 40+ generation while still maintaining the 'retro' style."

Having developed the prototype, Dimitrov has now turned his attention to the software. "Unlike many similar systems, Base-18 does not include an interpreter as part of the system software," he notes. "Instead, it includes a set of functions forming an operating system core (called Shell-18) that can be invoked from externally loaded user programs that are executing in native PIC18 binary code. It also supports installable drivers that can control additional boards with custom hardware. The built-in software includes a full FOS (File Operating System), system monitor, and also a unique and easy to learn and work with, line text editor. The file operating system includes a small internal flash-based drive, an optional RAM drive, and support for up to four externally connected SD cards or other storage devices."

The multi-card bus also offers a trick not often found on similar microcomputers: add-on boards can contain their own processors, which can either disable the PIC18 on the master board and take over or run alongside it — creating a multi-processor system limited only by the number of cards which can be inserted onto the backplane board.

As well as the above YouTube video demonstrating the Base-18, Dimitrov has published the project to Hackaday.io. He estimates that a cost-optimised bill of materials for the main board would come out at around £10 (approximately $13.)