Fan control questions

theycallmebruce · Post by **theycallmebruce** » Sun May 24, 2009 3:18 am

So, I'm mostly happy with my PC now. My Antec 300 build has five fans in total, and is quiet enough for my liking:

- Scythe S-Flex F for CPU heatsink, controlled from mobo CPU fan header (idles at 700 RPM)
- Scythe S-Flex F for rear case, controlled from mobo system fan header (idles at 700 RPM)
- Antec Tri-Cool 140mm (came with case), set to low
- Scythe S-Flex F for front intake, controlled from cheap Hong Kong fan controller (just a single knob mounted to a PCI slot cover), spinning around 700 RPM or so
- Stock fan in Seasonic power supply (dead quiet, never spins up very fast)

Now, my problem is, when I run HL2 engined games (Left 4 Dead, Portal, etc):
- I have to manually crank the 140mm Tri-Cool right up to high to prevent the CPU from overheating (very noisy and incovenient)
- The rear exhaust fan keeps spinning at just 700 RPM because the mobo temperature doesn't go up at all

So, my questions:
1) I'd really like to control three or even four fans from the output of the CPU fan header on the motherboard. I think this would overload it. Is there any fan controller hardware which can be used to "multiplex" the fan control from this header safely?
2) PWM vs analog control: Is it true that some fans are designed to work with PWM and others analog? What are the consequences of using the "wrong" control method with a fan? What control methods do the Scythe S-Flex F and the Antec Tri-cool 140mm support? I'm planning to borrow an oscilloscope and verify how all my current fan controllers work.

dhanson865 · Post by **dhanson865** » Sun May 24, 2009 5:36 am

I'd suggest you take a look at speedfan. You may be able to use it to control the fans based on CPU temp without changing where they are plugged in.

http://www.almico.com/speedfan.php

http://www.almico.com/speedfan438.exe

And for some thoughts on configuring it you can look at the questions and answers in this thread viewtopic.php?t=42526

theycallmebruce · Post by **theycallmebruce** » Sun May 24, 2009 10:34 pm

Thanks dhanson. I've used speedfan before just for temperature monitoring, but never for fan control. I'll check it out.

Anyone got an answer to my 2nd question, about PWM vs analog fan control?

kunaakos · Post by **kunaakos** » Mon May 25, 2009 1:55 pm

Hi There. I had similar problems, but my mobo has only one pwm header, and that's only for the cpu fan, and dumb as hell (long story). I opted for a scythe kaze-q fan controller, and non-pwm fans. It's cheap, looks great, and I mean great: it's made of black or silver finished aluminium, nothing flashy. just a few extra knobs without any led-bling, that's what I prefer. I have to crank ub the fan speeds manually, which can be quite annoying if you use BOINC as your screensaver, and come back after 30min to your pc, and a 75+ celsius gpu temp is waiting for you, if you left it at minimum speed.
the controller has 4 knobs, with 3-pin connectors. I don't know if these work with pwm fans or not. It worked with my 4-pin stock intel cooler, so it should... but I'm a newb, so don't trust me

I was also thiking about an AKASA 3-knob fan controller, which has two usb ports too, but it wasn't in stock.
if you're ok with manual control, I think both of these would suit you.

oh yeah, as far as i know, tri-cools aren't pwm (standard 3pin), I use an 80mm one with my controller, works great. but it's not silent at all... Ive also tried a 120mm tri-cool, and didn't liek that either (it was black, if it matters).

theycallmebruce · Post by **theycallmebruce** » Mon May 25, 2009 5:39 pm

Thanks for the info kunaakos.

I have a manual fan controller lying around from my old PC, so if I can't get automatic control going, I'll probably use that. I'd prefer auto control, but having knobs on the front of the PC would certainly be better than having to open the case to crank up the tri-cool and having the rear exhaust only spinning at 700 RPM!

ascl · Post by **ascl** » Tue May 26, 2009 1:24 am

Check the motherboard manual or whatever doco you can find. I remember seeing (on the guru3d gigabyte forums) a claim that the mobo fan header on my board could support up to 1 amp, which worked out to about 3 fans. Obviously your board is going to be different... but try and find out, cause you may just be able to chain 3 fans off it (depending on the fans too).

EDIT: My mobo has 2 controllable headers, which I use speedfan to control one of and allow the bios to control the CPU fan. The 2nd header I have tried chaining 2x 2000rpm 120mm fans and it was fine.

theycallmebruce · Post by **theycallmebruce** » Tue May 26, 2009 5:44 am

Good advice.. RTFM! I did, but unfortunately it doesn't state a maximum load for that header.

But, I did find something else that confused me. The CPU fan and sys fan headers are both four pin headers. But the pinouts are different according to the manual!

CPU FAN
pin 1 - GND
pin 2 - +12V / Speed control
pin 3 - Sense
pin 4 - Speed control

Sys fan
pin 1 - GND
pin 2 - Speed control
pin 3 - Sense
pin 4 - +5V

I would have expected the pinouts to be the same?

xen · Post by **xen** » Sun May 31, 2009 3:09 am

My fan header pinouts are slightly different as well:

Mainbord: Gigabyte GA-MA78GM-UD2H

CPU header
pin 1: GND
pin 2: +12V/speed control
pin 3: Sense
pin 4: Speed control

Sys fan header
pin 1: GND
pin 2: +12V/speed control
pin 3: Sense
pin 4: Reserve

Because it is a 4-pin header, I would think the Sys fan header supports PWM speed control, however the 4th pin goes unused according to this specification, and also, in BIOS, I am unable to select either Voltage or PWM for speed control, as I can with the cpu fan header. This leads me to think that only Voltage control is available for the Sys fan header.

I'm trying to decide what fans to purchase. To PWM or not to PWM, that's the question. The mainbord has two 4-pin headers (CPU, SYS) and one 3-pin header (NB). The sys-header may be a 3-pin in disguise.

The Ninja2 I'm going to buy will carry a 3-pin fan and naturally should go to the CPU fan header. The 92mm rear exhaust can either go to the NB header or (if cable long enough), to the Sys header.

But if the Sys header doesn't support PWM, then i'm not sure putting a PWM fan to it, is a good idea. I'm gonna have to ask Gigabyte.

theycallmebruce · Post by **theycallmebruce** » Mon Jun 08, 2009 9:53 pm

Thanks for the follow up xen. Let us know what you find out from them.

As soon as I remember to take an oscilloscope home, I'll probe the pins and find out exactly what the mobo does.

xen · Post by **xen** » Tue Jun 09, 2009 11:58 am

Gigabyte's answer wasn't very illuminating:

Whether the system fan speed control function is supported will depend on the system cooler you install.
According to the System Fan pin definition the Pin 2 has Speed Control.

So basically this support tech is saying that only voltage control is supported. (How can any fan not support voltage control?)

I already ordered a PWM fan. The motherboard and the rest of the order should arrive within a couple of days. After I have everything installed, I'll see what kind of speed control option there are.

If the sys fan header doesn't support PWM control, i'll most likely just connect the PWM fan to the CPU header

.

theycallmebruce · Post by **theycallmebruce** » Fri Jul 03, 2009 7:08 am

OK, so I tested the pins with a scope and here is what I found (only tested the first three pins on each header, my fans only have three wires):

CPU:
pin 1 - GND
pin 2 - Analogue voltage control (approx 6V for me at idle)
pin 3 - RPM sense (12V/0V pulses)

System fan:
pin 1 - GND
pin 2 - Analogue voltage control (approx 5V for me at idle, BIOS set to "Auto" for sys fan control method)
pin 3 - RPM sense (12V/0V pulses)

Still doesn't tell me what load the CPU fan header can take, so I'm going to try asking Gigabyte tech support. In the past they have been less than helpful though. I've received some blatantly false answers from them...

Broadleaf · Post by **Broadleaf** » Fri Jul 03, 2009 10:12 am

I have operated multiple fans from the cpu fan header. It works great. The spcr article "http://www.silentpcreview.com/article69 ... html#sflex" indicates that the S-Flex SFF21F that they tested used only 1.05 watts at 12 volts which is 88ma and much lower that than the scythe spec'd 200ma. The stated current requirement is probably the worst case startup current draw. Hopefully Gigabyte will come up with exact data, but I wouldn't hold my breath for that. The common word is that cpu fan headers will put out up to 500ma in order to support the fans on the 125 watt cpu's. The factory supplied fan on the Pentium 840EE is rated at 420ma.

Broadleaf · Post by **Broadleaf** » Fri Jul 03, 2009 4:34 pm

I suggest this experiment:

- put 2 of the Scythe S-Flex F fans on the 2 front panel locations and connect them to the cpu fan header.
- connect the Scythe S-Flex F on the Ninja to the system fan header.
- leave the side, top and rear fan positions empty.

theycallmebruce · Post by **theycallmebruce** » Sat Jul 04, 2009 8:53 am

Thanks for the info Broadleaf! Given the info there, I'm feeling confident to run two fans off the CPU header.

I will try your suggested experiment. Initially I'll wire the 2 front fans up to straight 12V because I don't have a cable to split the CPU fan header yet. You suspect there is not enough air being sucked into the case I guess?

In case it's important:
- My case sits on its side
- I have blocked off the side vent (which is actually at the top in this orientation)

Broadleaf · Post by **Broadleaf** » Sat Jul 04, 2009 10:15 am

You can get enough air sucked into the case with only a single fan blowing out the back.
The challenge is to get the system reasonably quiet and non-annoying at idle. You can build
a quiet PC doing the things that you are doing. Two slow fans mounted on the front of the
Antec 300 will be closer to your ears but they might generate less noise sucking in though
the grills rather than blowing turbulent air at the exit grills.

I had supposed the common placement of a standard mini tower case on the floor away from the
ears with the noise generating rear chassis fan furthest from the ears.

My P180 case sits on the floor and the top fan grill is blocked off. The 4 fans in my system are:

* the stock cooling on the Sapphire HD 3850 video adapter.
* an Antec tri-cool set to lowest speed in the lower chamber.
* a Scythe Slip Stream (Kaze-Jyuni) 120mm Case Fan, Ultra Low Flow, 500 rpm connected to a
constant 12 volts from the power fan header mounted on the on the Scythe Ninja CPU Cooler.
* a Scythe Gentle Typhoon 120mm 1,150rpm Silent Case Fan on the rear location with a 2.5 cm
(1 inch) duct in between the fan and the chassis grill to give the turbulent air time to
moderate before hitting that nasty cheap steel stammping rear grill. This fan is connected
to the cpu fan header for temperature controlled variable speed.

For your case orientation I would use the rear and top locations if they are further from your ears.

Fan control questions

Fan control questions

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