Firewire Compatility/Support in PCs.

I have searched fairly extensively to find out what will determine whether a system will support IEEE 1394 (Firewire) or not. Firewire card adapters say that you need Win 98 SE or better. However, that can’t be the only thing I have 2 systems thatwon’t recognize the card running SE, and one with ME, none of which will recognize the card. I have a PIII system with a new Gigabyte MB that recognizes the card fine. I am figuring that it must be at the motherboard, chipset, CMOS and Processor levels. Does anyone know where I can get definite info on what where processors, chipsets and such will begin supporting Firewire?