kernel hangs on detecting slave drives

[milan]

Hi,

I have a new server running 4.8 but i can't add any slave drives. the kernel hangs with :
ad3: READ command timeout tag=0 serv=0 - resetting
ata1: resetting devices ...

i tried different drives, different ordering but it always hangs when detecting the slave on either bus.  my BIOS detects it and i also tried some BIOS tweaks but no luck. using GENERIC kernel. any hints?

my mboard is:
http://www.supermicro.com/PRODUCT/MotherBoards/GC_SL/X5DEi.htm                  

much thanks-
milan