What is the maximum data transfer in PCI express?

The First-generation PCIe transfers data at a 2.5 GT/s (gigatransfer per second) signaling rate per lane. The PCI Special Interest Group (the industry organization that maintains and develops the various PCI standards) recently announced PCIe version 2.0 which increases the signaling rate to 5 GT/s per lane

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First-generation PCIe is often quoted to support a data rate of 250 MB/s in each direction, per (x1) lane. This figure is a calculation from the physical signaling rate (2.5 Gbaud) divided by the encoding overhead (10 bits per byte.) This means a sixteen lane (x16) PCIe card would then be theoretically capable of 250 MB/s * 16 = 4 GB/s in each direction

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PCIe 2.0 doubles the bus standard's bandwidth from 2.5 Gbit/s to 5 Gbit/s, meaning a x32 connector can transfer data at up to 16 GB/s in each direction.

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PCIe 2.0 delivers 5 GT/s but employed an 8b/10b encoding scheme which took 20 percent overhead on the overall raw bit rate. By removing the requirement for the 8b/10b encoding scheme, PCIe 3.0's 8 GT/s bit rate effectively delivers double PCIe 2.0 bandwidth. The final PCIe 3.0 specifications, including form factor specification updates, may be available by late 2009, and could be seen in products starting in 2010 and beyond

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