The PCI-e x16 is a graphics card slot. The PCI-e x1, can be also used for graphic cards, but not common. The PCI slot can be used for many different types of cards.....graphics, sound, SATA, TV tuner, etc.
*shrug* I dunno... I'm pretty sure that PCI-E allows more bandwidth, anyways, so x4 PCI-E might still be better than AGP x4...
Also, I think that I was wrong. I think PCI-E x4 and PCI-E x8 are speeds that PCI-E x16 runs at, under certain circumstances... I know x16 is actually x8 on some SLI motherboards.
there's 4 types of pci-express two types of pci (pci and mini-pci) and not sure but 3 types of agp. Pci-express x16 is generally the primary graphics card if in sli/crossfire this is downgraded to 2xcards 8xpci-express. the 4x and 8x can be used for tv tuners and I have seen some sound cards which use this slot and recently i found some extra cpu units which you can plug in. Pci-expressx1 is for simple things virtually the same as pci just faster transfer rate is for general things like raid adapters, network cards everything which comes on usb is normally available as pci or pci-expressx1. Agp Is a dedicated graphics slot which was the old standard it is expensive to upgrade and the choice of cards is limited, not worth having compared to pci-express.
PCI Slots 
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