PCI and AGP slots have been replaced with PCI-E slot (PCI-Express). There are different types of PCI-E buses:
PCI Express 1x (250 [500] * MB/s)
PCI Express 2x (500 [1000] * MB/s)
PCI Express 4x (1000 [2000] * MB/s)
PCI Express 8x (2000 [4000] * MB/s)
PCI Express 16x (4000 [8000] * MB/s)
PCI Express 32x (8000 [16000] * MB/s)
I hope that's what you meant :)
