If you have to replace the Main Control Board in the Drive you can replace the EEprom from one Board to another and do a Re-init. If that doesn't work and you end up having to init the Drive and the Miprom 21 CPU, you should copy the Drive, and the CPU Parameters. You will also have to install a new Floor Table, as an init wipes out everything to Default. The Prom Chip is not interchangeable. A service Tool should give you a lot more info than F 2.