7900 board on a 9900?

Hey guys, so my 9900 board went bad (I think static charge fucked it up or something… ( was cleaning the capping station and when I turned it on it just wouldn’t boot up). I replaced the main board with a 7900 board I had lying around, and it worked! Had to solder one wire in place (non-ribbon cable, just 3 stranded wires) where there was a clip-port on the 9900 board that was left unsocketed / no clip on the 7900 board. I finally got it to comply and be happy and we’re back in business… but of course, it thinks its a 7900 now. I tried loading the NVRAM from the 9900 board onto the printer using the service program, but no luck. Also tried to see if I could load 9900 firmware onto it, but it won’t let me… Any way to do this, or will I really just need a 9900 board?