X99S SLI PLUS - HDs in SATA5 and SATA6 dont show

Hi

I just bought a new motherboard for a work pc.

I wanna do 6 disk raid 10 in SATA port 1-6. Bios detects disk 1-4 but not 5-6.

Identical disk, identical cables, identical everything. If I move them to port 7-8 they show, but these ports dont support ...