Is a PWM capable fan necessary for speed control?

[Nessism]

Need a new CPU fan since the old one sets off the alarm; it starts very slowly until it warms up - sleeve bearing Yate Loon fan, one of the orange ones. Want to get a more durable fan this time and want the system to adjust the fan speed depending on temps, but unsure if a PWM capable fan is needed or a regular 3 pin fan w/rpm monitoring is all that's necessary? Motherboard is an ABIT P35-E, which has PWM. Also could use a fan recommendation - up to $25 or so. Can't find a lot of fans with RPM monitoring listed in the specs so that's got me confused too. I have lot of various fans with 3-pin connectors and some have RPM monitoring and some don't. How to tell when buying a fan?

Thanks in advance for any help offered.

 

[coffeejunkee]

Ok, if you want the motherboard to control the fan according to the mobo's internal fanprofiles (just like it would control the stock cooler) you need a 4-pin pwm fan. I know Scythe and Noiseblocker sell 4-pin pwm fans but many other brands stick to 3-pin.

The alternative is to use Speedfan, a program that can control 3-pin and 4-pin fans based on your own wishes. But Speedfan can only control fans connected to the mobo and then only if that connector is wired for speed control. Sadly not every mobo has controllable 3-pin connectors. Fex. the 3-pin fan connectors on Gigabyte mobo's cannot be speed controlled. MSI and Asrock do better in this department.

The second part of your question is harder to answer. Personally i've never come across a 3-pin fan that could not be speed controlled but i guess they exists. I know for sure Zalman and Thermalright 3-pin fans can be controlled and I would recommend the latter. Very quiet, good airflow and nicely sleeved.

 

[superccs]

I thought you could use a 3-pin and run the fan speed through the bios fan controls. If you use a 3-pin you can set the highest fan speed you want the fan to spin by setting a high and low voltage value (based on temp thresholds).

I never had any luck with Speedfan on my old ABIT IP35 pro XE

 

[NYHoustonman]

I thought you could use a 3-pin and run the fan speed through the bios fan controls. If you use a 3-pin you can set the highest fan speed you want the fan to spin by setting a high and low voltage value (based on temp thresholds).

Yep, although it depends on the motherboard (I've seen some that don't offer this feature). I would think most boards will have a 4-pin PWM connector for the CPU fan and 3-pin connectors for all case fans, and 3-pin fans won't be adjustable if used with a 4-pin connector as the motherboard assumes any fan attached there supports PWM (which is entirely different from lowering the voltage to control speed a la 3-pin).

Looking at the standard pinout, I'd think every 3+ pin fan includes RPM monitoring.

 

[coffeejunkee]

Well, it's true that Speedfan has to recognize the sensorchip on your motherboard. If it doesn't Speedfan won't be able to do anything. I've never had trouble using Speedfan with Asus, MSI and Gigabyte mobo's but Abit might not be supported. Easy way to find out is to just install Speedfan and look under configure > advanced to see if it recognizes the sensorchip.

If Abit mobo's indeed allow you to control 3-pin fans through bios settings as described above you wouldn't really need Speedfan. But on all the mobo's i ever used there were only very rudimental options for setting fanprofiles.

 

[Modelworks]

Whether it is 3 wire or 4 wire, PWM is used . The other way to lower speed is linear and that just waste power as heat and is really inefficient so is not used. PWM is turning on and off the fan for periods of time like plugging in a fan and turning the switch on and off repeatedly to control the total speed. The 3 wire and 4 wire both use the same technique just implement it differently.

With 3 wire you have ground, power, RPM. The motherboard controls the fan by supplying it with power that the board turns on and off to control the speed, it reads the fans speed using the RPM wire. The 4 wire have ground, power, RPM , PWM. The motherboard provides power at the full amount all the time and reads the RPM wire. The PWM wire is pulsed by the motherboard and the circuit on the fan controls the final speed.

The main benefit for manufacturers is that 3 wire fan control requires them put power mosfet on the board to control the output. 4 wire fans remove that requirement and put the mosfet on the fan. The reason for this is cost, and because using a fan too large for the mosfet on a 3 wire board will burn out the mosfet. If the mosfet is bundled inside the fan that will not happen.

 

[Nessism]

Checked the manual and apparently the MB will regulate the fan speed with either a 3-pin fan and a 4-pin PWM fan. My bad for not checking more carefully before posting here.

Any pros and cons of 3 pin vs. 4 pin for cpu fan control? And since the fan is going to be regulated down during low load conditions so noise shouldn't be a big issue, should I buy a higher speed fan, like a 2000 rpm jobby, and just let the MB throttle it down?

Thanks to all offering assistance.

 

[Modelworks]

Checked the manual and apparently the MB will regulate the fan speed with either a 3-pin fan and a 4-pin PWM fan. My bad for not checking more carefully before posting here.

Any pros and cons of 3 pin vs. 4 pin for cpu fan control? And since the fan is going to be regulated down during low load conditions so noise shouldn't be a big issue, should I buy a higher speed fan, like a 2000 rpm jobby, and just let the MB throttle it down?

Thanks to all offering assistance.

Main benefit of having a 4 pin fan is you can usually use a fan that has a higher current rating than motherboards that are 3 pin only.

Would buy the fan that outputs what I need at the noise level I need.

 

[Nessism]

Been researching fans and one thing I noticed is the bearing types vary a fair bit both in type/technology, and in expected lifespan. The better fans have MTBUF ratings in the 100,000 hr. range compared to 30,000 for lesser fans. I wound up ordering a CM R4 Excalibur since the specs and price are good: fan has PWM, and the performance/noise ratio was good as referenced by that overclocker.net fan test stickied here. Also ordered a few low speed YL's to have around as backups to the Antec units that come on their cases these days.

Took a close look at those Sythe GT's and S-flex fans, since they both have a high MTBUF, but these fans don't come with PWM so they got the pass.