PCI IRQ conflict?

[Chris Cappuccio <chris_(_at_)_empnet_(_dot_)_com>]

I have three Intel EtherExpress PRO 100B cards in a machine that is used
for routing...

fxp0 at pci0 dev 14 function 0 "Intel 82557 Fast Ethernet LAN Controller"
rev 0x04: irq 5
: Ethernet address 00:a0:c9:92:f2:8f, irq 5
fxp1 at pci0 dev 15 function 0 "Intel 82557 Fast Ethernet LAN Controller"
rev 0x04: irq 9
: Ethernet address 00:a0:c9:92:f4:4c, irq 9
fxp2 at pci0 dev 16 function 0 "Intel 82557 Fast Ethernet LAN Controller" 
rev 0x04: irq 10
: Ethernet address 00:a0:c9:92:f2:92, irq 10

But I also have an Adaptec 2940UW in the same machine...

ahc0 at pci0 dev 13 function 0 "Adaptec AHA-2940 Ultra" rev 0x00: irq 5

What kind of conflict could this create with fxp0?  Both fxp0 and ahc0 are
in use right now on the machine, so I guess the IRQ settings are of little
consequence.. Am I forcing the cards to choose the same IRQ with the
Legacy ISA vs. PnP ISA/PCI IRQ choices in the BIOS? Does this really
matter, etc....

-chris