PCI Express is a high-speed serial computer expansion bus standard for connecting high-speed components. It replaces the old AGP, PCI and PCI-X bus standards, and has been adjusted and improved many times. PCIe 1.0 was first released in 2002. In order to meet the growing demand for high bandwidth, different versions have been launched successively. There are currently five different PCIe standards: PCIe 1.0, PCIe 2.0, PCIe 3.0, PCIe 4.0, and PCIe 5.0. The transmission rate doubles every generation, and PCIe 6.0 will be released soon.
There are currently five available versions of PCIe cards: PCIe 1.x, PCIe 2.x, PCIe 3.x, PCIe 4.x, and PCIe 5.x. The new version of PCIe 5.x was just released in 2019, and its performance is better than before. Several versions are better. PCIe 6.x is expected to be released around 2021.
It is worth mentioning that all PCIe card versions are backward compatible, which means that any version of PCIe cards and motherboards can work in the mode of the lowest version. The table below shows the comparison of transmission rates between 5 traditional PCIe versions (take the original version n.0 as an example).