PCIe 2.0
PCIe 2.0 (Peripheral Component Interconnect Express 2.0) is the second generation of the PCI Express interface standard, introduced by the PCI-SIG (PCI Special Interest Group) in 2007. This version doubled the data transfer rate of its predecessor, PCIe 1.0, increasing the per-lane bandwidth to 500 MB/s in each direction, or 1 GB/s for a full duplex connection. With up to 16 lanes in a single slot, a PCIe 2.0 x16 connection offered a total bandwidth of 16 GB/s. This improvement enabled better performance for GPUs, RAID controllers, and other high-speed peripherals.
https://en.wikipedia.org/wiki/PCI_Express
The enhancements in PCIe 2.0 were achieved through improved signaling and protocol optimizations, while maintaining backward compatibility with PCIe 1.0 devices and motherboards. This ensured a seamless transition for manufacturers and users, allowing them to adopt the new standard without replacing their existing hardware. The increased bandwidth of PCIe 2.0 made it suitable for emerging technologies at the time, such as high-performance GPUs and SSD storage solutions, which required faster data transfer rates to meet growing computational demands.
https://pcisig.com/specifications/pciexpress/base
PCIe 2.0 remained a popular standard for several years until the introduction of PCIe 3.0 in 2010, which further doubled the bandwidth. Despite newer standards, PCIe 2.0 is still in use in legacy systems and certain embedded applications. It laid the foundation for the rapid development of high-speed interfaces in modern computing and remains an important milestone in the evolution of the PCI Express standard.
https://www.tomshardware.com/reviews/pci-express-2.0,1915.html