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I'm putting together a 1U rackmounted PC. I have a blower cooler for the CPU, but the chassis has no fans at all.

What would be the correct way to orientate the CPU cooler? With the air blowing in the direction of the power supply, or across the motherboard?

I'm also slightly worried that the cooling wont be adequate.

The CPU being used is an AMD Athlon II X2 255. Is the lack of case fans likely to be a problem?

The two options: enter image description here

The CPU cooler: enter image description here

The chassis:

enter image description here

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All airflow in rack mountable hardware should take air in from the front and blow it out of the back. Neither of your proposed orientations are ideal. I wouldn't even run a normal PC without at least one case fan, never mind a 1U server.

You should monitor the temps with speed fan or something similar if you're unsure whether or not a single fan is adequate. In all likelihood, it won't be.

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Thank you for the advice! Do you know if having exhaust air from the CPU going right over the motherboard or left in the direction of the PSU would be better? – Acorn Oct 1 '11 at 13:53
@acorn neither. Like I said, in through the front out through the back. If you're trying to stick commodity hardware in a 1U case without proper cooling, you are going to have problems. – MDMarra Oct 1 '11 at 13:55
It doesn't matter, it will only make hot air circulate inside the chassis, but it won't be able to go outside and be replaced by fresh air without case fans. – Massimo Oct 1 '11 at 13:55

Does the power supply at least have a fan? I hope so. If this is the case, then your best bet would be to blow hot air towards the PSU, which will (hopefully) blow it out of the chassis.

I agree with others, though: without case fans, airflow will very likely be too small to replace the hot air which will build up inside the chassis.

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Yes, the power supply does have a (tiny) fan. I suppose that's some air movement at least! I'll see what the temperatures do, and will probably end up sticking a couple of fans in the case. – Acorn Oct 1 '11 at 14:01

YOu will overheat. The orientation does not matter- you NEED fans in the case, or the air gets stuck in it. 1u is very small for natural air flow, esepcially given that there is no way for the heat to get out on top.

Sorry, this may work for a low power CPU that does not require active cooling, but one that requires a blower.... you just kill the harware through environmental overheating.

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Damn, thanks for the heads up. Seems crazy that a 1U case would be sold with No Fan For Low/No Noise.. – Acorn Oct 1 '11 at 13:55
No, it can work. Put in a nice low power atom board and there you go. Those small cpu's dont even have active coolers. But any normal 100 around watt system WILL overload. If you are lucky you can put one bwtween two "real" servers (and hope they keep cool enough), but normal stuffing - whow. Seriously, standding behind the computer rack in my data center the air coming out of the racks is HOT. – TomTom Oct 1 '11 at 17:29

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