UNDERSTANDING THE PCIE INTERFACE
SSDs are very fast and the SATA interface that many consumer SSDs currently use isn’t providing enough bandwidth to fully maximize an SSD’s potential. SATA in its current iteration provides just 6Gbps of bandwidth. After taking encoding inefficiencies into account, you are looking at about 4.8Gbps or 600MB/s, which also explain why most SATA-based SSDs currently top out at around at that speed. Now, the PCIe interface offers significantly more bandwidth. The latest version, PCIe 3.0, offers roughly 984MB/s per lane. This in turn means that the fastest PCIe-based SSDs today, which supports PCIe 3.0 x4, enjoy a maximum bandwidth of roughly 4GB/s - that’s six times more than SATA 6Gbps. PCIe 2.0, on the other hand, serves up 500MB/s per lane. As a result, PCIe 2.0 SSDs are usually slower than PCIe 3.0 SSDs.