A thesis by Jian – Xiong Shao, 1983, titled OUP/M – A 6502 Operating system, contains a floppy disk based operating system for the 6502. It is modelled after CP/M and follows the same design principles.
In the development of OUP/M, an OSI C-3 microcomputer system was used. This system consists of a 6502 CPU, a dual 8-inch floppy disk drive, a console, a printer, and 56 K bytes of RAM.
On this machine all I/O is memory mapped and address space layout has to be taken into consideration.

For years only the document was available, archived on archive.org, with the source in the document.
Jian – Xiong Shao did not publish more 6502 code, further implementations are unknown.

See the OUP/M page for sources and binaries found on osiweb.

This article is written by Jeff M. Nay, about his experiments to restore a KIM-1 to working order. The challenge was to address the second 6530-002 in this setup at another address then the onboard 6530-002 RRIOT.The experiment was a success, the 6530-002 is indeed in a bad state, the ROM is corrupt and it had to be replaced.The KIM-1, from a friend, was in a bad state. The repair was a success also. He was able to get this old KIM-1 working again, after only having to replace, the 6502 CPU, the 6530-002 RRIOT Chip with a Corsham 6530 Replacement board, all 8 Memory Chips and the U17 7406 inverter. Read the article here