After the server did a thermal shutdown this afternoon, I decided to lower the CPU multiplier from the factory specified 12.5x to 12.0x, lowering the resulting clock speed from 1667 to 1600, which isn’t that noticible. I also pulled the machine out from under the desk to give it better air circulation. Then I discovered the real problem: The rear fan is wired backwards.
- Black is the case
- Orange is power components
- Purple is data processing components
- Dark Teal is CPU heat sink
- Light Teal is fans and airflow
Okay, I’m nowhere near as graphics-talented as Chad, but here’s my 5-minute MSPAINT drawing of my server’s case layout.
Astute observers will note that there is very little clearance between the CPU heatsink and power supply. They will also note that the hot air from the CPU doesn’t get nicely pulled out the back by the rear fan, which is instead sucking air into the case.
A better flow would be to have the large 120mm fan in the front pulling air across the hard drives and onto the I/O cards (which it currently does), and the rear fan (80mm) pulling the now-heated air out the back, including the hot air off the CPU. The power supply does its own cooling since I can’t find any way to incorporate it into the overall airflow.
Now, I’d say that the guy who designed this machine is an idiot. And that would be true, since I designed this machine. The components are all used and since I had zero budget to build this thing, I did what I could. But I could have done better in the direction of the rear fan.