Editing PCI Express (section)

=== PCI Express 2.0 <span class="anchor" id="2.0"></span> ===
[[File:Rosewill-USB3-PCI-Express-Card.jpg|thumb|A PCI Express&nbsp;2.0 x1 expansion card that provides USB&nbsp;3.0 connectivity{{Efn|The card's [[Serial ATA#Standard connector|Serial ATA power connector]] is present because the USB&nbsp;3.0 ports require more power than the PCI Express bus can supply. More often, a [[Molex connector#Disk drive|4-pin Molex power connector]] is used.}}]]

[[PCI-SIG]] announced the availability of the PCI Express Base 2.0 specification on 15 January 2007.<ref name="PCIExpressPressRelease" /> The PCIe 2.0 standard doubles the transfer rate compared with PCIe 1.0 to 5{{nbsp}}GT/s and the per-lane throughput rises from 250&nbsp;MB/s to 500&nbsp;MB/s. Consequently, a 16-lane PCIe connector (x16) can support an aggregate throughput of up to 8&nbsp;GB/s.

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 work, with the other being v1.1 or v1.0a.

The PCI-SIG also said that PCIe 2.0 features improvements to the point-to-point data transfer protocol and its software architecture.<ref name="UaYlc" />

[[Intel Corporation|Intel]]'s first PCIe 2.0 capable chipset was the [[G35 (chipset)|X38]] and boards began to ship from various vendors ([[Universal abit|Abit]], [[Asus]], [[Gigabyte Technology|Gigabyte]]) as of 21 October 2007.<ref name="wHHTf" /> AMD started supporting PCIe 2.0 with its [[AMD 700 chipset series]] and nVidia started with the [[nForce 700|MCP72]].<ref name="gL2GQ" /> All of Intel's prior chipsets, including the [[Intel P35]] chipset, supported PCIe 1.1 or 1.0a.<ref name="mUQKD" />

Like 1.x, PCIe 2.0 uses an [[8b/10b encoding]] scheme, therefore delivering, per-lane, an effective 4&nbsp;Gbit/s max. transfer rate from its 5&nbsp;GT/s raw data rate.

==== PCI Express 2.1 <span class="anchor" id="2.1"></span> ====
PCI Express 2.1 (with its specification dated 4 March 2009) 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. The increase in power from the slot breaks backward compatibility between PCI Express 2.1 cards and some older motherboards with 1.0/1.0a, but most motherboards with PCI Express 1.1 connectors are provided with a BIOS update by their manufacturers through utilities to support backward compatibility of cards with PCIe 2.1.