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The PCIE 2.1 card will operate normally on the PCIE 1.0 or 1.1 but at the full bandwidth given by the PCIE 1.0 or 1.1PCI Express 2.1 supports a large proportion of the management, support, and troubleshooting systems planned for full implementation in PCI Express 3.0. However, the speed is the same as PCI Express 2.0.
PCIe 2.0 motherboard slots are fully backward compatible with PCIe v1.x cards. PCIe 2.0 cards are also generally backward compatible with PCIe 1.x motherboards, using the available bandwidth of PCI Express 1.1. Overall, graphic cards or motherboards designed for v2.0 will work with the other being v1.1 or v1.0.
The PCIE 2.1 card will operate normally on the PCIE 1.0 or 1.1 but at the full bandwidth given by the PCIE 1.0 or 1.1PCI Express 2.1 supports a large proportion of the management, support, and troubleshooting systems planned for full implementation in PCI Express 3.0. However, the speed is the same as PCI Express 2.0.