Apple Mac Pro (Early 2009) - Manual (Page 57)

Chapter 3 Making a Good Thing Better 57
Note: If you install different-size DIMMs in your Mac Pro, follow the order in the table. If
the DIMM configuration you install doesn’t provide optimized performance, the
Memory Slot Utility appears onscreen and recommends an improved configuration.
To use the utility again, go to /System/Library/CoreServices/Memory Slot Utility.
5 Install the DIMMs by aligning them in the DIMM slots and pushing both ends of the
DIMM down until the tabs are vertical and the ejectors snap into place.
NOTICE: To avoid damaging the DIMM, hold it by the corners and don’t touch the
gold connectors or other components.
Ejectors Notch Connectors