> That is indeed tiny...

Even RP2040 is fairly large as far as microcontrollers go. The widely used STM32F103 is a single 72 MHz Cortex-M3 core with 20 KB SRAM and 64 KB flash, for example. Even smaller parts aren't uncommon.

I know. But they won't run PC emulators unless the programmer is truly heroic.

I have worked on a slower Cortex-M3 than that. I've also worked on 8051 variants and on ST-62 (called "ST6 architecture" in the link below). My first computer was a ZX81 with a 16KB RAM pack.

https://en.wikipedia.org/wiki/ST6_and_ST7