RVPC – Open Source Hardware Board

I was curious how this thing did video. As you might expect, it's done by bit-banging the VGA RGB output pin from an IRQ. A time honored tradition. Here's the code in the Tetris demo: https://github.com/OLIMEX/RVPC/blob/main/SOFTWARE/Demo-Tetri...

With only 2kB RAM, the tetris demo implements what seems to be a 18 or 36-line screen with 21 characters per line. The bitmap for the next line is generated after blasting the bits out for the previous line.

Like some classic game consoles, this leaves most of the "vertical blanking period" for running your main game-or-whatever logic.

What's great about this board is the built in connectors & software to use it. And the fact you can build it yourself if you know how to wield a soldering iron. And it's a 32-bit microcontroller. On the other hand, its capabilities are limited by the small flash & SRAM: it has less RAM than an Apple I did! (but more flash than the Apple I had ROM, and RISC-V code density probably trumps 6502 code)