Warning: Wall of Text. I don't typically have to post many threads asking questions, but when I do I try to be as detailed as possible. There will be a TLDR at the end.
Note: I'm not an overclocker. I posted this here because this is the air cooling subforum and I figured it's the best place to put this. Sorry if it's in the wrong place
I've been looking high and low over the past few days but I'm looking for some general cooling advice. I've always stuck with stock case fans, stock cpu heatsink/fan combos, and always done pull from the front push from the back without any troubles in the decade or so I've been building my own systems.
Motherboard: ASUS M5A99X EVO
CPU: AMD FX-8120 Zambezi
Current system was built in January
Recently my CPU started running hot, being that it's summer now I figured the rise in ambient temp is too much for the stock fan to keep up, so the other day I ordered a Cooler Master Hyper 212 plus along with a second 120mm fan, the Blademaster 120mm PWM fan, after reading some threads here, along with a 4-pin splitter since I only have one CPU fan connector and both fans should run at the same RPM at all times. It'll arrive tomorrow, and I intend to put it in a push/pull configuration with it exhausting towards the back case fan.
I also want to replace the back case fan with a 120mm, which brings me to my main question....
My main concern is:
Do I need to match the CFM of the Heatsink's fan for optimal cooling to exhaust the hot air, or can I just get close? It seems to me, that if the heatsink is throwing, say, 20 CFM towards the back case fan, the back case fan should also be throwing 20 CFM out the back in order to keep up, or else it'll cause problems.
Is this a correct assumption? Would I want one that does MORE than the CPU to be safe, since it's also exhausting other hot air?
My other concern is: Should I buy a case fan with a 4-pin connector and connect it to the motherboard, or should I put it on a molex via an adapter? Will it run @ 100% at all times on a molex connector?
If I put it on my motherboard's only 4-pin CHA_FAN connector (Labeled CHA_FAN1. _FAN2 and _FAN3 are 3-pin) will the motherboard automatically know to scale the case fan along with the CPU fan, or will they operate differently? Would there be a setting in BIOS? (I'd check, but the computer is currently in pieces awaiting the new fan's arrival)
And my last concern: If I should attach it to the 4-pin, what happens if it's a 3-pin fan? I assume the 4th pin is fan speed control, without the motherboard being able to control the fan's speed will the fan automatically go to 100%?
TLDR; Does my exhaust fan on the case need to match or be greater than the CFM of the CPU fan blowing towards it, and should I connect the fan to the motherboard or to 4-pin molex? If it's a 3-pin fan in a 4-pin slot on the mobo, what happens?
For the first question, you can get away with different RPM of CPU's fans as long as the CFM is similar. I would recommend that the exhaust fan to be faster than the CPU's fans so none of the heated air is recycled in the case.
I've wondered this for a while. I have the 212 Plus with the Blade Master as push and two slower NZXT fans (pull and rear case fan). The NZXT fans are rated at 1300 RPM and around 47 CFM. I recently did a test by moving the Blade Master fan around and recording max temps after running Prime95 for an hour.
Blade Master as push, max temps hit 65C
As pull, max temps hit 66C
And as rear case fan, temps hit 67C
The testing was done at night with a house fan blowing towards the front of the case (Phantom 410) from six feet away. Intel i5 2500k at 4.5 Ghz with core voltage at 1.290. Fan speed was set to 100% on all fans. Also my case has 8 fans (two 120 mm front intake, one 120 mm bottom intake, one 140 mm side intake, one 140 mm fan on hard drive cage, two 140 mm top exhaust and one 120 mm rear exhaust).
I often wonder how much lower temps would be if i had Blade Master fans for push, pull and rear case fan. I would like to hope it'll be 2-3C cooler.