The PS32 board is the two board stack that is in the steam upgrade kits and also is used to replaced failed PS/2 boards. It consists of a special PS/3 board (different layout), and an interface board that makes it look like a PS/2 board in regard to interfaces. Specifically, instead of LED's, you use 6V bulbs, and instead of the PS/3 tach reader, you use the older PS/2 tach reader. Here's a thread by Marty F that has lots of pictures of the PS32 board.
