Mastodawn

One of my favorite features of the Baochip-1x is the BIO. It's an I/O coprocessor that is based on the PicoRV32, with custom register extensions to allow direct access to GPIOs from the ISA.

Read more about the BIO at this blog post: https://www.bunniestudios.com/blog/2026/bio-the-bao-i-o-coprocessor/ I go in-depth into the architecture and its trade-offs relative to the PIO, and conclude by working through a couple of coding examples.

Show thread

Luke Wren

@bunnie This is a really elegant design. PIO was definitely warped by too much emphasis on single-cycle operation at low fmax, and the assumption that you always have a nearby (specifically bus-synchronous) CPU to poke and prod it. This makes much more sense for your system and choice of frequency ratio.

Show thread

bunnie 1d ago

@wren6991 thanks! I also really enjoyed analyzing and understanding the PIO, it's a really interesting point in the design space and there's a lot of clever ideas in there.