Guide To Build a PC from Scratch - Step 3: How To Install A CPU and FAN (Heatsink)

ProcessorAfter you have installed the PSU, the CPU and the heatsink/fan may be installed on the platform before the motherboard is placed in the computer case. The processor and motherboard are sensitive to electrostatic discharge so make sure you wear antistatic wrist strap and DO NOT touch the CPU contacts at any time. When you are installing a used CPU, clean the CPU and the base of the heatsink with isopropyl alcohol. Doing this removes all traces of old thermal compound. The surfaces are now ready for a new layer of thermal compound. Follow all manufacturer recommendations about applying the thermal compound.


Follow these instructions for CPU and heat sink/fan assembly installation:


  • Align the CPU so that the CPU sockets aligned with Pin 1 on the CPU socket. Place the CPU gently into the socket.
  • Close the CPU load plate and secure it in place by closing the load lever and moving it under the load lever retention tab.
  • Apply a small amount of thermal compound to the CPU and spread it evenly.
  • Align the heat sink assembly retainers and place the heat sink onto the CPU socket and tighten the heat sink onto the motherboard.
  • Connect the heat sink power cable to the motherboard.

CPU fans use either 2, 3 or 4-pin power connectors. CPU fans and Motherboard's fan sockets are backwards compatible (you can connect a 4-pin fan onto a 3-pin header or vice versa). The speed of fans can be controlled by varying the voltage from BIOS. The 4-pin fans use PWM (Pulse-width modulation) control system to operate at higher performance.