iMac G3 down converter boards


Does anyone know if the down converter board from a G3 iMac DV SE (500 MHz) will work on the 700 MHz G3 iMac SE? The PDF tech manuals that I have show two different boards, the components on the boards look slightly different. But I can't find any parts numbers to confirm that they actually do function differently.

While we're at it, just what exactly does a down convertor board do?