Question about HighPoint Rocket 640L

I also use it without RAID, only with AHCI as an extension of the too-scarce onboard ports under Windows 10 Pro and am very happy with it. There are drivers for Windows Server 2012 on HighPoint's website, but I haven't tried it out myself.

I use this card as a pure HBA without RAID, and since it is AHCI compliant, it is quasi transparent to the OS. I use it under FreeNAS and the disks are recognised as if they were plugged directly into the MB. This was also necessary for me, as all slots are already occupied by the MB. Plug them in and you're done, without any configuration or additional drivers.
However, I have read in various places that a hardware RAID with this card only results in problems. For this, you should rather use the RocketRAID series, which is closely related in name. For FreeNAS/ZFS with software RAID, however, this is not a problem.
As long as no hardware RAID is needed, I claim it should work, but I do not guarantee it...