PC World’s Jon L. Jacobi has taken the time to examine a bunch of currently available M.2 SSDs in an attempt to separate the chaff from the wheat when it comes to delivering really fast read and write performance. The results are pretty interesting – guess what? Not all M.2 drives are equal.
M.2 SSD compatibility has become increasingly more common in recent times with almost all high-end and even mid-range motherboards supporting the newer, more discrete drive technology. M.2 drives remember, have direct access to PCIe Gen 3, offering way more potential bandwidth for fast SSDs compared to a traditional SATA connection.
Keep in mind that M.2 PCIe, and PCIe drives in general, are relatively new technologies. The SM951 AHCI, only a single generation removed from the XP941 AHCI, is dramatically faster. Both are x4 PCIe, but the XP941 is PCIe Gen 2 (500MBps per lane), while the SM951 is PCIe Gen 3 (1GBps) PCIe. But even the x4 PCIe 2.0 provides 2GBps of bandwidth, so that can hardly explain the entire disparity.