Apple Xserve (Early 2008) - Manual (Page 39)

Chapter 2 Installing or Replacing Components 39
About PCI Cards for the Xserve
The Xserve accepts PCI cards that meet these specifications:
Slot 1
 64-bit PCI-X 133 MHz cards (using a PCI-X riser)
 32-bit or 64-bit 33, 66, or 100 MHz PCI or PCI-X cards with 3.3 volt universal signaling
 x8 PCI Express cards using a PCI Express riser
 6.6 inch maximum length
 25 Watt maximum power consumption
Slot 2
 x16 PCI Express 2.0 cards
 9 inch maximum length
 25 Watt maximum power consumption