There are many on PC. I used Speccy the most known. Also nice FPGA projects.
In meanwhile, I could ported more emulators to the Teensy 4.0 using a PSRAM module.
Recently added PC engine, Gameboy, Sega Master System, Megadrive and AtariST are using it.
https://github.com/Jean-MarcHarvengt/MCUME/blob/master/README.md
The list becomes bigger every day: Atari 2600,Odyssey,colecovision,Atari5200,Vectrex,NES,PCEngine,Sega Master System,Sega Game Gear,Sega Megadrive and Gameboy.
And for the computers: ZX81and spectrum, Atari800,C64,AtariST, 8086 XT.
Only theTeensy 4.0 could do them all!
https://youtu.be/j2sKw7KYpEo