The Other schrieb: Maybe it is. It is if the XEON's are new enough. BUT: the 860 is an pretty old intel chipset (iirc the professional version of the 850), so chances very are high that your XEONS are pretty old and do _not_ support 64bit. if your xeons have less than 2.8 GHz, they are for sure not 64bit capable. this has nothing todo with the word size of your prozessor. 64bit PCI slots are just "professional", and achieve higher thruput than 32bit ones. (not totally true; 64bit PCI slots also natively do 64bit adressing, while the 32bit ones normally only do 32bit adressing. 64bit adressing could also be done w/ the 32bit PCI bus, but very few 32bit PCI cards do support this. But OTOH This only does matter if you have more than 4 GBytes of RAM, and want to do DMA to physical memory above the 4GB barrier. In this case you need to use an IOMMU, or it will simply not be possible.) 64bit PCI slots also run commonly with 66MHz and 3.3V, which is indicated by the key that is no near your case. you can plug combatible 32bit PCI cards (they have two notches, one for the 5V key, and one for the 3.3V Key) in an 64bit slot, and you'll take advantage of the 66MHz. As stated before, most likely, you can't.