Recognizing pci devices by kernel

Hi,
Maybe someone noticed the effect that linux kernel recognizes the same
hardware - for example ethernet cards different between the system
restart. I mean if we have 2 or more eth cards and the have some ethX
names, after restart they will receive quite different ethX names.
I wonder what is the reason that linux kernel reports the same pci
devices in other order between the restarts?
Anyone knows that reason?

I know that it may be solved using udev, but I'm interested in some way
to always get the same pci device recognition order.

ne