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some fan powering questions

post #1 of 4
Thread Starter 
A few fan power questions.

Getting a couple of San Ace 1011s. Gonna use one as exhaust and one on CPU heatsink (Venomous X).

Is it advisable to power this high-cfm fan through the cpu fan socket on my motherboard (evga 780i FTW)? Might have one or two other, low/mid-cfm fans on the board. (The exhaust fan's gonna go on a fan controller or a psu molex, definitely isn't going on mobo.)

Or, would it be ok to attach both fans to a Y cable (2 ins, one out), and power them both through a single connector, which I'd either be connecting to a fan controller (Sunbeam Rheobus), or a psu molex? Would they be underpowered...or worse?

And finally...Is it possible to bypass my motherboard cpu fan socket, and leave the socket empty...and still get my computer to start up? Just can't seem to find any bypass control in BIOS or elsewhere. (I'm assuming the board won't allow start up if that socket is empty, that appears to be SOP, but I haven't actually tried yet.)

It looks like using a 3pin-to-molex adapter with a separate, yellow-wire out (RPM monitor) that I would plug into the cpu fan socket might work - it's the adapter that comes with a lot of fans - but then I don't think I'd get to plug the fan into the controller, or otherwise control fan speed.

(Still sort of confused re: 3pin-to-molex adapters with that separate yellow wire/3pin out. Folks say you can only monitor RPM with it, not control speed...but why would you want to see RPM w/out being able to control it? WHY?!?)

Any help is greatly appreciated.

btw the San Ace 1011s are coming from svc.com. They have a bunch.
Edited by seward - 3/16/11 at 1:42pm
post #2 of 4
On 3-pin fans:

Pin 1 = power
Pin 2 = power
Pin 3 = RPM monitoring

Speed is controlled by varying the voltage to the fan.

4 Pin fans:

Pin 1 = power
Pin 2 = power
Pin 3 = RPM (?)
Pin 4 = PWM signal.

Pwm fans ALWAYS get the full 12 volts. The pwm signal from the board tells the 'smart' chip in the fan what speed to run at.

I would not recommend more than one fan per header. What I would do is plug both of them into a fan controller (ONE per header). You can daisy chain as many as you want on molex, unlike the board the molex connectors can provide much more amperage....probably a whole 12v rail's worth.
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The Butthurt Box
(21 items)
 
   
CPUMotherboardGraphicsGraphics
Intel Core i5 2500K P67 Professional AMD Radeon HD 6950 unlock NVIDIA GeForce GTX 460 2gb 
RAMRAMHard DriveHard Drive
G.Skill Ripjaws G.Skill Ripjaws Intel X25-V Seagate Barracuda 
Hard DriveOptical DriveOSMonitor
WD Goflex USB 3.0 24x DVD R/W DL Win7 Ultermate 64 Acer 20in 1600x900 
MonitorMonitorMonitorKeyboard
Compaq 20in 1600x900 17in Dell 1280x1024 19in Gateway 1280x1024 Razer Blackwidow mech w/ cherry MX blues 
PowerCaseMouseAudio
Kingwin LZ-750 HAF 932 + sound activated lights Logitech G500 Rosewill USB headset 
CPUMotherboardGraphicsRAM
Pentium 4 3.2ghz w/ HT HP Intel IGP 4gb Mushkin DDR2 
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80gb sata WinXP Pro HP OEM HP Small form factor 
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post #3 of 4
Typically up to 1 amp is safe. You can check your manual or contact tech support for what the max amps are for your specific MB. Hooking both fans up to a fan controller is probably the better option.

You can use the 3-pin to molex adapters which will power the fan and allow you to monitor the RPM (yelllow wire) through the MB fan header. This does not provide speed control.

Most BIOS have an CPU fan alarm you can disable, but I'm not sure what or where the settings are for your MB. Hopefully someone with the same MB will know.
post #4 of 4
Thread Starter 
Thanks guys, +1 all...Yeah, I think I'm gonna go with one fan per header, exhaust on a controller and cpu heatsink fan on the mobo. I haven't tried starting my rig with no fan plugged into the cpu fan socket, and for all I know it just gives a warning and starts anyway. Couldn't find anything in BIOS that seemed to disable any sort of cpu fan alert - UNLESS it's the error reporting thingie. I may plug another fan into it (an intake or something), and see if that keeps it happy.
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