A hardware interface for SATA drives using two lanes of PCI Express (PCIe) in order to increase the transfer rate over regular SATA. Motherboards came out in 2014, but few drives materialized.
Of course, the SATA interface doesn't have anywhere near the same levels of bandwidth and timings as PCI Express, which is why NVMe SSD rule the roost these days. Take the best gaming M.
While SATA was the standard for many years, eventually it created a bottleneck for faster storage. PCI Express provides a faster interface speed than SATA and it's slowly replacing it as the new ...