Is device resource depletion *cumulative* ??

'Never heard of resource depletion for add-on devices until it happened to
my own PC. This concerns PCI expansion slots specifically. There's a chunk
of memory allocated to each add-on device, and an IRQ assignment, yes? My PC
has 3 PCI slots and I've been juggling a variety of add-ons in them for
years. Occasionally I have switched a device to a different slot for
reasons, and devices have come and gone.

Finally I must've gone too far! I removed a TV/FM card, forgetting to
explicitly direct Windows XP to Uninstall it first. Then I moved a modem
card from another slot to there. Windows was unable to init the modem,
balking about "insufficient resources" and the need to free up other
devices' resources. So I Uninstalled the modem, put back the TV/FM card
(seemlessly, for the New Hdwe Wizard didn't even pop up), then Uninstalled
it explicitly, removed it and returned the modem card and after that it
initialized and worked just fine.

I'm just curious if the problem was just about one device in one slot, or
was it a cumulative effect of precious resource depletion from years of my
perhaps occasionally being sloppy about the removal of PCI cards. I wish to
know the truth. Thank you!