CalDigit RAID Card - Manual (Page 20)

20 A. MacPro
1.24 Install the PCI bracket and tighten the thumb screws
1.25 Slide the memory cards back into the DIMM cage (4 Core Mac
Pro)
1.26 Make sure the rear latch is up. Install the drive modules and slide
in the drive modules
Note: In order to boot up the system correctly, please install the
system drive to the first left drive slot in your Mac Pro.
PCI bracket