RP2040 and RP2350 PIO makes producing VGA signals criminally easy.
But many other µCs can do it too, at least to some degree. Even Atmels.
But many other µCs can do it too, at least to some degree. Even Atmels.
It's at least partially a matter of timing: Oxide was picking its initial hardware in roughly 2020, and the RP2040 wasn't released until 2021.
A handful of people have done ports, e.g. https://github.com/oxidecomputer/hubris/pull/2210, but I expect to stick with STM32s for the foreseeable future – we've got a lot to do, and they're working well enough!
Probably the best history on the choice of going with ARM comes from here: https://news.ycombinator.com/item?id=28989138
The internal RFD on the SP's design still talks about choosing RISC-V, and I don't think (or am simply bad at using search) that the move ended up being in an RFD.