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Why PWM fan headers?

Jurrunio
By Jurrunio
in Cooling
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Go to solution Solved by Damascus,
10 minutes ago, Jurrunio said:

so you mean it's not actually necessary, it's just a bit better?

Pretty much, its a quality of life thing.  

11 minutes ago, Jurrunio said:

Funny enough, the white LED on it changes brightness according to the fan speed as well (probably because both are directly related to voltage).

This is another good reason ^

Posted

I know 4pin fans and fan headers support PWM which is used to control their speed, but why? My nearly 3pin-only motherboard (1 4pin. 5 3pin) can still control fan speeds of all but 1 fan header through voltage control.

CPU: i7-2600K 4751MHz 1.44V (software) --> 1.47V at the back of the socket Motherboard: Asrock Z77 Extreme4 (BCLK: 103.3MHz) CPU Cooler: Noctua NH-D15 RAM: Adata XPG 2x8GB DDR3 (XMP: 2133MHz 10-11-11-30 CR2, custom: 2203MHz 10-11-10-26 CR1 tRFC:230 tREFI:14000) GPU: Asus GTX 1070 Dual (Super Jetstream vbios, +70(2025-2088MHz)/+400(8.8Gbps)) SSD: Samsung 840 Pro 256GB (main boot drive), Transcend SSD370 128GB PSU: Seasonic X-660 80+ Gold Case: Antec P110 Silent, 5 intakes 1 exhaust Monitor: AOC G2460PF 1080p 144Hz (150Hz max w/ DP, 121Hz max w/ HDMI) TN panel Keyboard: Logitech G610 Orion (Cherry MX Blue) with SteelSeries Apex M260 keycaps Mouse: BenQ Zowie FK1

 

Model: HP Omen 17 17-an110ca CPU: i7-8750H (0.125V core & cache, 50mV SA undervolt) GPU: GTX 1060 6GB Mobile (+80/+450, 1650MHz~1750MHz 0.78V~0.85V) RAM: 8+8GB DDR4-2400 18-17-17-39 2T Storage: HP EX920 1TB PCIe x4 M.2 SSD + Crucial MX500 1TB 2.5" SATA SSD, 128GB Toshiba PCIe x2 M.2 SSD (KBG30ZMV128G) gone cooking externally, 1TB Seagate 7200RPM 2.5" HDD (ST1000LM049-2GH172) left outside Monitor: 1080p 126Hz IPS G-sync

 

Desktop benching:

Cinebench R15 Single thread:168 Multi-thread: 833 

SuperPi (v1.5 from Techpowerup, PI value output) 16K: 0.100s 1M: 8.255s 32M: 7m 45.93s

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Since PWM uses pulses of 12 volts, the fan won't stall at low speeds as easily as when using DC control, such as using 5V to achieve a lower speed on a 12V fan.

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Pwm ia a more elegant solution

Want to custom loop?  Ask me more if you are curious

 

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5 minutes ago, thegreengamers said:

Since PWM uses pulses of 12 volts, the fan won't stall at low speeds as easily as when using DC control, such as using 5V to achieve a lower speed on a 12V fan.

indeed, my fan do stall at 10% (in Speedfan), but not at 15%. Funny enough, the white LED on it changes brightness according to the fan speed as well (probably because both are directly related to voltage).

 

5 minutes ago, Damascus said:

Pwm ia a more elegant solution

so you mean it's not actually necessary, it's just a bit better?

CPU: i7-2600K 4751MHz 1.44V (software) --> 1.47V at the back of the socket Motherboard: Asrock Z77 Extreme4 (BCLK: 103.3MHz) CPU Cooler: Noctua NH-D15 RAM: Adata XPG 2x8GB DDR3 (XMP: 2133MHz 10-11-11-30 CR2, custom: 2203MHz 10-11-10-26 CR1 tRFC:230 tREFI:14000) GPU: Asus GTX 1070 Dual (Super Jetstream vbios, +70(2025-2088MHz)/+400(8.8Gbps)) SSD: Samsung 840 Pro 256GB (main boot drive), Transcend SSD370 128GB PSU: Seasonic X-660 80+ Gold Case: Antec P110 Silent, 5 intakes 1 exhaust Monitor: AOC G2460PF 1080p 144Hz (150Hz max w/ DP, 121Hz max w/ HDMI) TN panel Keyboard: Logitech G610 Orion (Cherry MX Blue) with SteelSeries Apex M260 keycaps Mouse: BenQ Zowie FK1

 

Model: HP Omen 17 17-an110ca CPU: i7-8750H (0.125V core & cache, 50mV SA undervolt) GPU: GTX 1060 6GB Mobile (+80/+450, 1650MHz~1750MHz 0.78V~0.85V) RAM: 8+8GB DDR4-2400 18-17-17-39 2T Storage: HP EX920 1TB PCIe x4 M.2 SSD + Crucial MX500 1TB 2.5" SATA SSD, 128GB Toshiba PCIe x2 M.2 SSD (KBG30ZMV128G) gone cooking externally, 1TB Seagate 7200RPM 2.5" HDD (ST1000LM049-2GH172) left outside Monitor: 1080p 126Hz IPS G-sync

 

Desktop benching:

Cinebench R15 Single thread:168 Multi-thread: 833 

SuperPi (v1.5 from Techpowerup, PI value output) 16K: 0.100s 1M: 8.255s 32M: 7m 45.93s

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10 minutes ago, Jurrunio said:

so you mean it's not actually necessary, it's just a bit better?

Pretty much, its a quality of life thing.  

11 minutes ago, Jurrunio said:

Funny enough, the white LED on it changes brightness according to the fan speed as well (probably because both are directly related to voltage).

This is another good reason ^

Want to custom loop?  Ask me more if you are curious

 

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11 hours ago, Jurrunio said:

so you mean it's not actually necessary, it's just a bit better?

It can be better but it can also be worse. Due to how pwm powers a fan using pulses, a ticking noise can occur that isn't present when using dc. This can result in a less smooth noise profile. 

There are cases where a 4pin pwm variant will be better than 3pin dc due to lower minimum rpm and vice-versa due to the difference in acoustics.

If you ever need help with a build, read the following before posting: http://linustechtips.com/main/topic/3061-build-plan-thread-recommendations-please-read-before-posting/
Also, make sure to quote a post or tag a member when replying or else they won't get a notification that you replied to them.

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PWM fans have several advantages over voltage control, including the aforementioned wider speed range. Another advantage is the ability to control more fans per fan header than one can do with voltage control as long as the power is taken from the PSU instead of the header.

Jeannie

 

As long as anyone is oppressed, no one will be safe and free.

One has to be proactive, not reactive, to ensure the safety of one's data so backup your data! And RAID is NOT a backup!

 

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