I ran CrystalDiskMark on my SATA 3 connected Samsung Evo 850 SSD, and it reported a 1839MB/s sequential read speed, and 1676MB/s write speed. SATA 3 has a maximum of 750MB/s and Samsung says at best it would perform at 540MB/s. Is the software wrong, why is it so fast?
Apparently some of the Samsung SSD use a technology called RAPID mode. As far as I can tell this is basically a huge cache using the PC's memory. The effect you see from this in benchmarking is a dominance of memory transfer speed over SATA transfer speed especially on sequential (and therefor predictable) operations.