I put a bios and boot code up on Howard Harte's site some time ago. This was source code for CP/M 2.2 (and it's in 8080 MAC/ASM assembler). If you have a working system, it's not too difficult to get this running. Again, the source code can be downloaded from Howard's site. As it exists, it's configured for 8". Should not be difficult to modify for 5.25". It works, I'm actually running it on a 16FDC (I believe that it will work on a 4FDC also).