If the card has a bridge chip (AGP<->PCI-e), then the PCI ID value is hardwired into it and the name of the card will still GeForce although it will behave as a Quadro.
If the card is without bridge chip (native), than you can change the PCI ID and the card will become a perfect clone.
Because of that, the AGP native NV40 and NV48 AGP cards and the PCI-E native NV43 A2 PCI-E cards can be softmoded perfectly (look and feel of a Quadro).
On the other side, the NV40(NV45) PCI-E and NV43 AGP cards cannot be completely softmoded (only feel like Quadro), the name will still be GeForce although the cards will behave like Quadros.
Real world performance differences between AGP8X and PCI-E 16X are practically nil.
IMHO, the real benefit of the PCI-E today is the SLI possibility. The other PCI-E advantages (symmetric bandwith) will not be used for at least a year in the future...
mrka kapa...