My HP-XW6400 workstation running windows-10 64-bits while booting shows AHCI bios is not installed

[Greatheatt_2011]

My HP-XW6400 workstation running windows-10 64-bits while booting shows AHCI bios is not installed

[DGroves]

this bios message on boot up is normal and by design (ahci still loads for the sata drives connected to the sata ports) 

first, make sure the bios is at the defaults of "RAID+AHCI"

it's caused when you do not have a CD/DVD optical drive attached to the sata port(s) why HP did not make the msg say ahci driver for optical device not loaded escapes me, perhaps the string was to long for the available bios space?

also, unless you require booting from the onboard LSI SAS/SATA ports (found along the bottom edge of the board)

disable the LSI bios in the 6400's Bios, doing so will speed up the boot times and any drives attached to the LSI ports will still be seen, but will not longer be a boot drive

[SDH]

To OP.... please specifically tell me how you know that the AHCI drivers are not installed.

For years now use of a Samsung SSD and using Samsung Magician to view AHCI status has reported false result.  That is one idea.

A second idea is that at least if W7Pro64 is installed with SATA emulation is set to IDE in BIOS the proper drivers for AHCI do not get installed.  I could test that here with a W10-activated xw6400 but I need to know how you are so sure the AHCI drivers are not present.