I just put a nice new Samsung 850 SSD drive into my Mac Pro 5.1 and noticed that it maxes out at 250MB/s write/read. The drive should be capable of speeds around 500MB/s, so the culprit here is surely SATA II port inside the Mac Pro.
My question is... do you know of any PCIe card that I could use to get SATA III in my Mac Pro? I do not need RAID capability, connecting just this one drive would be enough for me.
