Wow! Really pushes the capability of the RP2040 to add a Memory Management Unit for the external RAM and incorporate DMA and a VGA display. The PIO on this chip is amazingly flexible.
“ The PSRAM/HyperRAM PIO engine provides 42/32 MB/s (write/read) of memory bandwidth. Further, four PIO engines are used to provide four seperate read/write memory ports. This allows independent memory access for the emulated CPU, video DMA, and receive/send Ethernet traffic.”
They're like general-purpose Amiga Coppers. You can program them to control I/O lines and they will just do the I/O, independent of the CPU.
This emulator is probably just the beginning of really cool things that will be built with the Raspberry Pi Pico.