I looked around at several different places looking for the answers before i bought my new computer alot of sites talk about the motherboards of pci express being different then current agp. But if you look on ati's site there new RADEON X800 XT PLATINUM 256MB AGP that is being released on sept 20th in there product detail sheet it states.
Specifications
System Requirements
RADEON™ X800 PRO, RADEON™ X800 XT and RADEON™ X800 XT PLATINUM EDITION require a connection to your PC's internal power supply for operation. Consult your system builder or OEM to ensure your system has an adequate power supply. Otherwise, ATI recommends a 300-Watt power supply or greater to ensure normal system operation where a number of other internal devices are installed.
Intel Pentium 4/III, AMD Athlon 64/7K/Athlon XP with AGP 8X (0.8v), 4X (1.5V) or universal AGP 3.0 bus configuration (8X/4X) or PCI Express™ bus configuration
128MB of system memory
Installation software requires CD-ROM drive
DVD playback requires DVD drive
From my understanding there saying that the card will be agp/pci-e compatable.
Computers with pci-e slots are alreay out the sony vaio r series that i just purchased is running a pci express ati radeon x600 xt card. I already can't wait for the 20th to upgrade my card to bad i couldn't wait another month so i didn't have a x600 xt card in the closet collecting dust like all my older graphics cards