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Passively Cooled PC

Build your silent PC

This instruction shows you how to build a performing silent PC, that remains cool under full load, without the use of cooling fans.

Step 1: Verify limitations

Every design has its limitations. If the anwers of one of the questions below is Yes, this design is not for you.

  1. Do you wish to operate the PC at ambient temperatures above 40 degrees Celsius?
  2. Do you wish to overclock the PC?
  3. Do you wish to use powerful top-end graphics?

Step 2: Choose your favorite CPU

You may choose any CPU, that has a TDP of no more than 95W, and a maximum allowable temperature (Tcase) of at least 70 degrees Celsius.

Characteristics of CPUs can be found at the sites of AMD and Intel. Alternatively you can check the following CPU overview.

Step 3: Choose your graphics solution

Any graphics solution can be used. Unfortunately the most powerful videocards all come with fans, which generate noise. CPU integrated graphics are effectively cooled using the CPU cooler, but other solutions should also do well as long as there is lots of room for ventilation. Graphics components typically have much higher allowable temperatures than CPUs, which helps.

Step 4: Choose your mainboard

There are no specific requirement to the mainboard. However because cooling may be more critical than in a well ventilated case, it is advised to use a somewhat more advanced board. If available choose a version that allows a higher TDP than your processor requires.

Step 5: Choose SSD, RAM memory, power supply and DVD

Use SSD storage instead of a conventional harddrive
Use an entirely passively cooled power supply
Use an external DVD player, connected over USB, that can be removed whenever not needed.

Step 6: Dimension your passive CPU cooling solution

For the standard parts there are two options here:

  1. Scythe Orochi
  2. Scythe Orochi combined with Scythe Mugen mounting brackets for Intel socket 1155.

The Mugen mounting brackets are compatible with the Scythe Orochi cooler - my own setup makes use of this combination.

In order to effectively cool 65W or 95W, a chimney that extends 25 cm to 45 cm respectively above the cooler respectively, needs to be constructed on top of the horizontally oriented Orochi cooler. For optimal results, the sides of the cooler should be covered as well. The chimney can easily be created using heavy paper and duct tape.

Step 7: Case design

The mainboard will be positioned horizontally. The chimney on top of the cooler will rise quite some distance above it. As far as I know there is no standard case available that supports this setup. This means you have to build something yourself, maybe re-using an existing case.

Take care of

  1. little resistance to inflow of cold air at the lowest level
  2. little resistance to outflow of hot air at the highest level
  3. correct orientation of the power supply
  4. hot air from the graphics card or mainboard graphics should not be the cooling air for the PSU
  5. do not lead an unsupported chimney out of the case. This potentially acts as a cantilever that damages the mainboard
  6. assembly - installing the mainboard including cooler and chimney as a single unit is most easy

Step 8: Assembly

Assembly is needed to finalize your PC.

Step 9: Verification

It is advised to do the verification in the following order:
  1. find out how to read out the thermal sensors while running your OS
  2. verify values and maximum values in an idle situation
  3. start a heavy workload, and determine the gap between the temperature and the nearest limit. Bear in mind that CPU sensors may provide Tjunc instead of Tcase. The temperature limit for Tjunc is higher than the limit for Tcase, typically 80 degrees Celsius or above.
  4. determine the maximum operating temperature, by adding the gap to the ambient temperature
Note that temperatures may already reach high values under partial load because - opposed to fan cooling - this cooling solution is progressive.

Useful links

My PC
Other Designs