A PCI device optionally can support MSI (Message Signaled Interrupts) and/or MSI-X (Message Signaled Interrupts - Extended) interrupts. Even a device supports MSI or MSI-X, driver for that device may not support them. This can be due to either lack of support in OS or driver itself. Whether the driver has support for MSI/MSI-X or not, it is possible to find a device's support for MSI/MSI-X through its PCI configuration space. Run "pciconf -lvc" and find that device's info. Example: Neterion Xframe-II 10Gigabit Ethernet Adapter xge0@pci1:3:0: class=0x020000 card=0x602017d5 chip=0x583217d5 rev=0x02 hdr=0x00 vendor = 'S2IO Technologies' device = 'Xframe II 10Gbps Ethernet' class = network subclass = ethernet cap 05[40] = MSI supports 32 messages, 64 bit, vector masks cap 07[60] = PCI-X 64-bit supports 133MHz, 266MHz, 4096 burst read, 32 split This device suports 32 MSI messages.