silencing solutions, PWM and 3/4 pin fan questions

[roundabout]

Hi silent enthusiasts,

I have a question regarding fan RPM/noise management which I'm hoping you clever folks can help with...

First, here's the situation: I've built a new system (partially using advice from this forum) and am very happy with it but would like to decrease the fan noise a bit. I've done some research on this wonderfully resourceful site and have decided to purchase two Scythe S-Flex Fans (SFF21E and SFF21F) to replace the rear stock (TriCool) chassis fan and the somewhat noisy Coolermaster 120mm Rifle fan I temporarily have attached to the heatsink.

My question has to do with PWM and how I can use it to achieve my silencing goals or whether I should be using an alternate solution given my hardware. The relevant hardware consists of:

Antec P183 case
ASUS P7P55D-E motherboard
Thermalright Venomous X heatsink

Here is a diagram of my mobo with the fan connectors notated, borrowed from the ASUS manual -->



Any guidance on this topic would be terrific! You can read more details including some of my thoughts and questions on this topic as it might be helpful understanding where my ignorance lies.

Thanks!
Dave



[ optional reading ]

I'm looking to keep my box relatively cool, but also very quiet. (The idle temps with stock hardware were in the 48-50C range and I've been able to get that down to the mid-30s with the addition of the Venomous heatsink and CM fan). Now I just need to get the fans quieter. BTW, following some reviews and suggestions on the P183, I've disabled the top case fan and covered the grill and that has reduced the noise quite a bit.

For some reason only the CPU_FAN seems to support PWM. I was thinking I would use this connector for the Scythe CPU Fan but the fan only has a 3 pin connector, and the mobo calls for a 4 pin and the 4th pin is for PWM. Does this mean the 3 pin fan would not be adjustable using PWM and if so, how else can I adjust the CPU fan speed?

I've noticed many fans are sold with 3 pin connectors but advertised with 3 to 4 pin adapters but the 4 pin adapters are (always?) the large molex power connectors and not the small 4 pin connector that would plug into a motherboard. So, I'm uncertain how the 3-4 pin adapter helps in this case. Yes it supplies power, but can the molex PSU connector be used to modify fan speeds?

My mobo also has a 4 pin CHA_FAN1, but this does not appear to support PWM from the diagram. There are also the PWR_FAN and CHA_FAN2 connectors which are both 3 pin and appear identical in their function. I only want to have the 2 fans mentioned above in my system for now, so if I can successfully use these mobo connectors to adjust fan speed, that would be good.

I've read a bunch about changing fan speeds by alternating voltage and/or using BIOS settings or fan controllers, but I'm not sure what would make the most sense for my equipment. I'd like to not have to purchase too much additional equipment and instead use what I have already if that will achieve the (near)-silent computing goal. I've used the BIOS Q-FAN feature with limited success as it doesn't seem to alter the fan speed much for the CPU (maybe the CM fan doesn't support PWM?). I've also used Speedfan and it successfully changes fan speeds but doesn't properly report the RPM changes. I'm willing to do some modding to the PSU if necessary, but would prefer to not have to do that.

Thanks in advance for any guidance in my quest for a near-silent PC!

- Dave

[~El~Jefe~]

spend like 15 dollars and get a 3.5" bay 3 fan control that ignores PWM and just does voltage control.

worked for me since 2000

on board stuff sucks. boards just dont give proper feedback, enough control, or fast enough response.

My tip of futility and angst:

I noticed one day that I can just buy stuff and let creativity take a hike.

[Arbutus]

My Main System is currently in an Antec P180 spcr_edition Case with 3 Gelid Silent 12 fans on PWM y-adapters connected to the Cpu fan Header. I get quiet operation at idle and lots of airflow automatically on demand the CPU heats up. There are quieter fans than the Gelid Silent 12 PWM, such as the fan that accompanies the current Ninja and Mugen models, but my ASUS mainboard complains if the fan speed drops below 600 rpm.

[~El~Jefe~]

if you get a big enough heatsink, the fan speed wont matter as much as far cpu workload, the difference will be always within tolerance.

Huge Don King's for the win + rheobus controllers. set it to 6 volts and go to sleep.

I'm also trying to grasp your goal. I know your goal is not to playaround with a motherboard, but to cool some sort of processor in some sort of environment for some sort of time on task and for some application. I think that's missing to figuring out what you need?

or are you just asking bios questions?

also, are you using a 4-pin fan? motherboards default to voltage control OFTEN if you are using a non pwm fan on motherboard header. normally for that you use a Fan_1 header and just set temp control.

Of course, motherboard temps are always wrong so that wont help you not fry your chip.

bios controls for the loss....

[Das_Saunamies]

If you want the S-FLEXs, +1 for the controller as suggested by El Jefe. There's just no better option right now. The S-FLEXs are superb, had them for ages, never set a foot wrong.

If you want PWM, take a look at Arctic Cooling F12 PWM fans. I bought a couple recently and am pleased - they're not the best, but they're good bang for buck since they're cheap (8 euros here). They come with integrated splitters, but I find the solution a bit poor and added an Akasa PWM splitter cable that gave me more range and amperes to work with. Asus control on the P7H55D-M EVO gets the job done, finally (can set your own scheme up in OS, 20%-100% range, three stages).

The Arctic fans will be an interesting and affordable experiment if nothing else.

Links:
http://www.arctic-cooling.com/catalog/p ... 68&mID=342
http://www.akasa.com.tw/update.php?tpl= ... l=AK-CB002

[Arbutus]

.
I recently built a budget gaming system for a friend. The dual core CPU is overclocked from 2.8 Ghz to 3.84 GHz and the mid level Video card card also generates a high, but not excessive, amount of heat. I used a Scythe Mugen heatsink and put it all into an Antec Sonota case. I used only one Gelid Silent 12 PWM fan. This single fan does double duty by both getting the heat away from the CPU and moving room air through the chassis. The fan is mounted on the side of the heatsink adjacent to the rear chassis fan location and blowing towards the rear of the chassis. A 3.8cm duct was made out of a 120mm fan with the guts cut out and mounted on the rear chassis fan location. The CPU fan and the duct align well enough for most of the air to exit the chassis.

This cooling setup compared to normal configurations reduces noise in these ways:
=> There is only one fan making noise.
=> The fan makes less noise sucking air from the heatsink than blasting turbulent air at the heatsink.
=> The fan is inside the case and not at the edge of the case where it's noise would be more apparent.
==> Turbulent air from the fan has time to moderate before exit the rear of the chassis.
.

[roundabout]

Thanks for the feedback.

@El Jefe, a fan controller seems like a decent alternative to PWM, especially if it's more responsive and smoother as you said. Which rheobus fan controllers would you recommend?

BTW, I read this on the wikipedia page re: PWM while getting up-to-speed on the technology: "Variable-speed fan controllers for computers usually use PWM, as it is far more efficient when compared to a potentiometer or rheostat." If this statement is true, are there any negative effects of a fan controller versus PWM?

@Arbutus &
@Das_Saunamies, thx for the PWM y-adapter and splitter recommendations. The Akasa splitter you referenced DS looks pretty slick if I decide to go the PWM route.

I have a couple of additional questions regarding fan connectors in general, just to make sure I'm understanding this stuff correctly...

1) Is the 3-pin fan connector standard for motherboard connections?

2) Is the 4-pin (small) connector only seen on "PWM fans" ?

3) Is the PWM technology integrated in the fan itself, or is the PWM technology in the motherboard header, or both?

Thanks for the help!

[Arbutus]

1) Is the 3-pin fan connector standard for motherboard connections?
2) Is the 4-pin (small) connector only seen on "PWM fans" ?
3) Is the PWM technology integrated in the fan itself, or is the PWM technology in the motherboard header, or both?
.

.
.
1) The 3-pin fan connector is a standard on PC motherboards.
2) The 4th pin on the PWM fan connector is an extension of the 3-pin standard fan connector. The 4th pin is the PWM control signal. You may connect a standard PC fan to the original 3 pins. The 3-pin fan will run at maximum speed or if the mainboard has analog fan control as well as PWM control then the fan speed can be proportional to the CPU temperature changes. In this case the mainboard will vary the 12 volts downward according to some formula in order to decrease the fan speed as the CPU temperature decreases.
3) The PWM control signal travels from the mainboard to the PWM fan. PWM means Pulse Width Modulation and the signal is a square wave whose percentage on-vs-off time varies in response to the CPU temperature so that as the CPU gets hotter the on time percentage of the PWM control signal increases towards 100%.
.

[lodestar]

Is the PWM technology integrated in the fan itself, or is the PWM technology in the motherboard header, or both?

It's built into the motherboard chipset itself. Modern chipsets like the P55 do far more than those of 10 years ago. For example, by default when the system is at idle it will downclock the CPU and undervolt it as well, reducing power consumption and the amount of heat being generated. You will be using a multi-core CPU with this chipset, so another of its functions is to bring cores onto stream and/or engage the Turbo modes depending on the load on the system. The PWM fan speed is controlled by a series of temperature sensors which are monitored by the chipset. This includes Digital Thermal Sensors which are located on each core of the CPU.

So what a PWM fan will give you is low speeds at idle, typically around 500 rpm, and an automatic increase in fan speeds as system load increases. Since this is a CPU-temperature based system it will also take account of ambient temperature. With the right choice of PWM fan it is essentially a 'fit and forget' process. Your particular motherboard has PWM fan mode control. Set CPU Q-Fan Control to Enabled in the BIOS, and you then have a choice of Standard, Silent or Turbo modes. Choosing the Silent mode will minimize the idle speed, so you can have a quiet system with automatic fan control. If, despite this, you really do want to control the PWM fan speed, then software such as CPUID HWMonitor Pro will do this without the need to buy additional hardware.

[roundabout]

Cool, thx for the comments. It's very helpful.

Today I found a splitter that has 3x 3-pin fan connectors for 5V, 7V, and 12V which all connect to a single 4-pin molex power connector. I'm experimenting with the different voltages to see about temps and noise. I also picked up a PWM splitter (3 fans to 1 4-pin header) but don't have any PWM fans to test yet.

So far I just have a new S-Flex (1200 RPM) fan running on the 5V connector and mounted to the Thermalright Venomous X heatsink. Temps are relatively high and noise is relatively low. Will probably try 7V next. 12V seems a bit loud.

I might get a fan controller after all. Seems like it might be the best option for voltage granularity.

[Tetreb]

If haven't already you can try undervolting your CPU to lower temps too.