forgot that part:
Guys with memory problems add this to the grub.cfg:
set common_args_3617='disable_mtrr_trim syno_hdd_powerup_seq=0 HddHotplug=0 syno_hw_version=DS3617xs vender_format_version=2 console=ttyS0,115200n8 withefi elevator=elevator quiet syno_port_thaw=1'
Now I got:
total used free
Mem: 16034 260 15458 3 315 15560
Swap: 11665 0 11665
/proc/mtrr is editable even from a command shell: you can disable register records and/or write new values there this seems to be a Bios bug.
Adding disable_mtrr_trim disables it without losing any performance as far as I know.
Use this if you see your RAM as being reserved under Resource Monitor > Memory.