Asus AW1500-I5 - Manual (Page 32)

2-6 Chapter 2: Hardware information
The Intel ® Xeon™ processors require specially designed heatsink and fan
assembly to ensure optimum thermal condition and performance.
Follow these steps to install the CPU heatsink and fan.
2.4.3 Installing the CPU heatsink and fan
1. Place the heatsink and fan
assembly on top of the installed
CPU, making sure that it fits in
place.
2. Hook one end of the retention
bracket into the protruding tab on
the corner of the plastic retention
base. (The retention base comes
installed with the motherboard.)