Asus PCH-DL - Manual (Page 30)

2-12 Chapter 2: Hardware information
11. Press down the fan and air tunnel
assembly until the side rails slide
past the grooves and over the rail
stoppers. The protruding tab on
each corner of the air tunnel
should snap over the dents on the
retention mechanism.
12. Connect the fan cable to the
connector CPU_FAN1 on the
motherboard.
Fan cable
Fan connector
Rail stopper
Side rail
Protruding tabs
13. To install a second CPU and heatsink, follow the same procedure as in
the first CPU installation.
Make sure to connect to the
correct fan connector.
Otherwise, you will get a
warning message during
POST.
For the second CPU, make sure to connect the CPU fan cable to the
connector CPU_FAN2.