Apple Mac Pro (Mid 2010) - Manual (Page 59)

59 Chapter 3 Making a Good Thing Better
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 a better 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