was dropped in the final version of the standard. The standard allows 64-bit transfer for AGP8× reads, writes, and fast writes; 32-bit transfer for PCI operations. Unofficial variations A number of non-standard variations of the AGP interface have been produced by manufacturers. Internal AGP interface Ultra-AGP, Ultra-AGPII It is an internal AGP interface standard used by SiS for the north bridge controllers with integrated graphics. The original version supports same bandwidth as AGP 8×, while Ultra-AGPII has maximum 3.2GB/s bandwidth. PCI-based AGP ports AGP Express Not a true AGP interface, but allows an AGP card to be connected over the legacy PCI bus on a PCI Express motherboard. It is a technology used on motherboards made by ECS, intended to allow an existing AGP card to be used in a new motherboard instead of requiring a PCIe card to be obtained (since the introduction of PCIe graphics cards few motherboards provide AGP slots). An "AGP Express" slot is basically a PCI slot (with twice the electrical power) with an AGP connector. It offers backward compatibility with AGP cards, but provides incomplete support (some AGP cards do not work with AGP Express) and reduced performance—the card is forced to use the shared PCI bus at its lower bandwidth, rather than having exclusive use of the faster AGP. AGI The ASRock Graphics Interface (AGI) is a proprietary variant of the Accelerated Graphics Port (AGP) standard. Its purpose is to provide AGP-support for ASRock motherboards that use chipsets lacking native AGP support. However, it is not fully compatible with AGP, and several video card chipsets are known not to be supported. AGX The EPoX Advanced Graphics eXtended (AGX) is another proprietary AGP variant with the same advantages and disadvantages as AGI. User manuals recommend not using AGP 8× ATI cards with AGX slots. XGP The Biostar Xtreme Graphics Port is another AGP variant, also with the same advantages and disadvantages as AGI and AGX. PCIe based AGP ports AGR The Advanced Graphics Riser is a variation of the AGP port used in some PCIe motherboards made by MSI to offer limited backwards compatibility with AGP. It is, effectively, a modified PCIe slot allowing for performance comparable to an AGP 4×/8× slot, but does not support all AGP cards; the manufacturer published a list of some cards and chipsets that work with the modified slot. Compatibility AGP cards are backward and forward compatible within