I upgraded my old computer with a Samsung EVO 850. I did a clean Windows 10 installation.
Installed Samsung Magic and fixed all the AHCI settings. Now I have full 6Gb/s transfer speed.
However, my problem is Windows "Optimize Drives" tool wants to defrag my SSD like a hard drive. As far as I know, this is bad.
The rest of the OS works fine, and my 3rd party programs see that it's a SSD.
CPU: Intel Core i7 (4th gen)
Mobo: Asus P7P55DE_PRO