What does HackerNews think of bmc64?
A bare metal Commodore 64 emulator for the Raspberry Pi with true 50hz/60hz smooth scrolling, low input latency and better audio/video sync.
Language:
C++
Last time I wanted to fiddle with a C64, I just went and flashed bmc64 (https://github.com/randyrossi/bmc64) to an SD card. Even an original Raspberry Pi 1 does a decent job of emulating it.
Latency.
It doesn't matter how fast your emulator is, throughput-wise. Your operating system (and other stuff) sits between it and output and input devices. And usually adds multiple frames worth of latency. There's ways to improve this, certainly, but you won't get that experience "out of the box."
Now, it's also possible to accomplish this by running emulators "bare metal" or "close to the metal" like my friend Randy did with his BMC64 project: https://github.com/randyrossi/bmc64
You could boot BMC64 on the Pi: https://github.com/randyrossi/bmc64
In addition to the Interim Lisp system I mentioned in another comment, there are a number of bare-metal applications for the Raspberry on github (mostly ports of games).
I especially like this Commodore 64 emulator (also based on circle): https://github.com/randyrossi/bmc64