Question about CPU fans

[pirahna1]

I always thought CPU fans blew hot air away from the heatsink, but this (http://www.overclockers.com/tips1186/index.asp) puts me into the assumption that CPU fans blow air onto the heatsink. When I put my hand next to my CPU fan, I fell nothing, whereas if I put my hand next to my intake and exhaust fans, I feel air moving from the side that pushes air out, and nothing at the side that pulls air in.

I want to try this mod, but I'm not sure what my CPU fan is doing... It's an AMD X2 6000+ dual core (retail) if that helps any. Also, just to make sure, video card fans blow air away from them, right? I just want to be 100% positive before I go and create a vacuum and blow my PC up.

Thanks for the help!

[pirahna1]

Eh, I found a feather and tested things out.

My CPU pulls air in, along with my GPU and mobo GPU fan. I always thought all these devices blew air out.

Think I should disconnect my mobo GPU fan since I'm not utilizing it? Would it harm anything?

[Seditedi]

They blow air onto the heatsinks.
Should have 1 intake fan on case and one exhaust fan on case so that cool air gets pulled in and the hot air gets pushed out.

[Khamsin]

The fan blows cool air onto the heatsink, the same as when you fan yourself off on a hot day. Blowing air away from something only works when there's air coming in, e.g. when you open both windows in a car, or two windows in your house to generate some air flow. Opening just one window and blowing air out doesn't do much. And while there's air flow through the case, there's none through the CPU itself.

As seditedi said, you got fans sucking cool air into the case, and fans blowing hot air out, so that's how the CPU fan has cool air to blow on the heatsink in the first place. And by cool, it's not really "cool" by our standards, since the ambient system temperature inside the case is a bit on the warm side. But it's a lot cooler than the CPU temperature (or the hot air you can feel being blown out of the case).

[Myst]

if i understand correctly, the "GPU" fan you're referring to is in the side of the case. it's not going to affect your cpu much either way, but you should be concerned with it's primary function: which is cooling the GPU. i've had a video card overheat on me from lack of airflow, and it sucks. just dont make the same mistake i did and assume the 25mm $0.10 fan will be proficient.

[Skyylya]

You're heatsink is attached to the CPU itself so it can absorb the heat generated by the processor. The heatsink absorbs that heat and then your fan blows cool air onto the heat sink to cool it off so that it can absorb more heat from the CPU.

The fan on the side of your case can be helpful or counterproductive depending on the design of your case.

Air flow is very important, with the flow being the key part. You don't want 12 fans just randomly blowing air around in your case without proper flow of cool coming in, and heat going out. If you've got to many fans hurting the in/out flow, you'll end up just blowing hot air all around the inside of your case not effectively cooling anything.

Best kind of air flow is to have strong cool intake in the front and a strong exhaust in the rear with as little obstacle through the middle of your case that blocks that in/out flow which can happen if your fan blowing in from the side is to strong or point in the wrong direction.

[Kooldac]

If possible, a fan on the top of your case is also a good idea along with sides as warm air may be there. Plus the obvious intake/exhaust in front/back.

[SephYuyX]

Quick mockup of what how you should have a PC fan'd, a cooling system is always good too.

http://img124.imageshack.us/img124/1189/fansyc4.jpg
Two intakes on the front, one on the top, one on the side, with 2 outtakes on the back for the case.
For the motherboard, there's fans usually blowing on the CPU and the graphics card (not a part of the MB but you get the idea), some motherboards support fans for both the north and south bridge chips, and some also have support for ram fans.

[pirahna1]

Thanks for all the replies :D

Quick question though. A motherboard's integrated video card is what is called the South Bridge right? Since I have a stand-alone PCI-E video card, can I safely disconnect the fan that sits on top of the integrated video card heatsink, since I'm not utilizing it? Or does the PC still utilize it even with a stand-alone GPU card?

[SephYuyX]

It really depends on the MB, though video is usually done through the north or it's own chip. Both bridges are very important regardless as they do more than just video (north) or audio (south). Even if you have seperate chips/cards for those fuctions, those bridges are still be used to process some of those functions, and different ones all together such as other I/O and memory operations.