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How To: Properly Plan And Pick Parts For An Air-Cooled PC, Part 1

Airflow: Unique To Downward-Facing Blowers

Downward Blowers (Top-Down Coolers)

The boxed heat sink and fan combos you get from AMD and Intel are not particularly efficient because their airflow is not aligned with a vent in the chassis. So, they blow straight down onto the motherboard. On the upside, the motherboard's power logic gets a bit of cooling assistance. But it's up for debate whether that makes up for limited performance and more noise. We've noticed the boxed coolers from AMD are particularly guilty, barely pushing enough air to keep the 125 W processors running well, and often spinning at up to 6000 RPM, generating obnoxious levels of noise.

As with the other cooling setups, the rest of the components, the chassis, and the built-in fans play an important role when using downward-facing blowers.

The above machine receives insufficient active airflow. There’s no rear ventilation, and the graphics card blocks the effects of convection even further.

That's better! This setup allows even a retail boxed cooler to dissipate heat effectively.  

Assembly Options

Optimization with Side Ventilation

The often-slandered side fan actually makes a lot of sense if you're using a downward-facing blower, since cool air coming through the vents is blown right onto the CPU cooler's intake. Remaining components also stand to benefit from these vents, so they can really be worthwhile:

You can either choose to use a case with a big, slow, and quiet fan like the LC-Power Titus...

...or you opt for a model with a couple of 12-cm fans, like on this Enermax Hoplite:

  • compton
    After reading the charts of PSU placement and the GPU cooling diagrams, I'm even more convinced that my Lian Li PCA05-NB is a great solution. The motherboard is upside down, so that GPUs (In my case an axial fan gpu) faces towards the top. The CPU is now at the bottom back of the case and with the rear fan acting as an intake and not exhaust, you get great CPU cooling. The PSU mounts in the bottome front as well. The great part of this design is all the heat ends up in the top. As an option, you can vent the top to release the heat rising from the GPUs, but I like the case because it has very little venting. Through unusual case design and careful component selection I have an almost silent system - but with overclocked CPU and GPUs. The front fan is the exhaust, but has a bezel over it. With a few bucks worth of acoustic dampening material I can even hear myself think sometimes. I regard low temps and low noise output to be two sides of the same coin, but I know that many seem to not mind loud systems and mainly just care about temps. It's never been easier to build a near-silent system, even with high performance gear.

    If you plan ahead of time, you can make a super quiet and cool running system. It's easier to build a cool and quiet system from the start than retroactively go back and try to make a noisy (and/or hot) system quiet with great temps.

    I'll be waiting for article 2.
    Reply
  • Mark Heath
    Good timing as the Australian summer approaches. You guys in the US think you have it hot :S
    Reply
  • buzznut
    Guten hunger YAH!
    Reply
  • JOSHSKORN
    I want my next PC to be able to play Crysis AND make me hot dogs and Iced Frappuccinos.

    All kidding aside...curious though, the test setup is on AMD CPUs. What about Intel CPUs? I would assume many of the concepts are similar.
    Reply
  • 100100
    Finally! A definitive article on how to air cool effectively! :D
    Reply
  • frostmachine
    Great guide. I live in a perpetually hot n dusty place. This will come in handy.

    Would be better if there's some tips on dust management.
    Reply
  • beetlejuicegr
    heh i am just showing you a pic from my pc that the airflow is totally different because there is a watercooling system on the cpu, i hope that the picture is self explanatory for all.

    Reply
  • amirp
    Hey I have a question... for the PSU you say to not put it in upside down (ie. with it's opening facing up into the chassis..) but this is how I have mine in my ANTEC300 case since there is little room between bottom of case and the PSU if mounted right-side up. So what should I do?!!
    Reply
  • BulkZerker
    amirpHey I have a question... for the PSU you say to not put it in upside down (ie. with it's opening facing up into the chassis..) but this is how I have mine in my ANTEC300 case since there is little room between bottom of case and the PSU if mounted right-side up. So what should I do?!!
    PSU's don't pull that much air, normally. So unless your Unit kicks it's fan speed way up there then don't royy abotu it and do as suggested. If it doesn't work then you can always just flip it back to where it was.
    Reply
  • darkrydr3
    BeetlejuiceGr, your cpu core temps are pushing 70 or 90 degrees C... thats hot!
    Reply