Daisy chaining mixed 4-pin fans

Shrek · 2025-02-11T02:54:50+0000

When one daisy chains 4-pin fans, only one has the tachometer pin active (to avoid mixed signals), but what if one was to daisy chain mixed fans, say 120mm and 140mm, should one take the tachometer signal from the smaller or larger fan?

I have a case that takes a 120mm exhaust fan and on top can carry two 140mm fans, all to be controlled by a single 4 pin connector on the motherboard.

eidairaman1 · 2025-02-11T03:23:09+0000

Shrek said:
When one daisy chains 4-pin fans, only one has the tachometer pin active (to avoid mixed signals), but what if one was to daisy chain mixed fans, say 120mm and 140mm, should one take the tachometer signal from the smaller or larger fan?

I have a case that takes a 120mm exhaust fan and on top can carry two 140mm fans, all to be controlled by a single 4 pin connector on the motherboard.

Whats the max rpms for the 120 and the 140 mm?

Shrek · 2025-02-11T03:39:01+0000

2200 RPM for the 120 mm

1500 RPM for the 140 mm

nomdeplume · 2025-02-11T03:41:01+0000

eidairaman1 said:
Whats the max rpms for the 120 and the 140 mm?

He suggests a set of these were recently purchased. Yet to further an explanation of how "daisy-chaining" will be handled.

Short of it this doesn't work well if at all on a lower end board. BIOS will express it's disregards in one of a few highly suggestive manners.

Shrek · 2025-02-11T03:53:23+0000

Will the BIOS even know? it is getting a speed reading from one fan alone.

Dr. Dro · 2025-02-11T04:16:05+0000

Shrek said:
Will the BIOS even know? it is getting a speed reading from one fan alone.

No, and yes, it is. The problem with fans that while the voltage supply from the motherboard is the same, the speed that each motor will run at different speed.

Assuming a linear response to voltage supply, similar blade design and air throughput with a 12 volt input, a theoretical fan A runs at 2000 RPM and fan B at 2200 RPM, at 8 volts fan A will run at 1320 and fan B at 1450, this will obviously result in mismatched noise levels and possibly, a pressure imbalance. It's best to get similar fans that work as a set if it can be helped, or use a fan controller that allows for individual setting for each port.

nomdeplume · 2025-02-11T05:18:05+0000

BIOS handles the fan controller even if programming it is being overruled by third party software. The issue is cascading electrical responses the board doesn't expect will only extrapolate with mixed fans. Honestly, lower end boards are questionable powering and feeding a signal into even two identical fans drawing less than .5A peak.

Legacy board designed to barely support intake/cpu/exhaust are not a good platform to control amount of fans modern cases will mount.

eidairaman1 · 2025-02-11T07:49:49+0000

Shrek said:
2200 RPM for the 120 mm

1500 RPM for the 140 mm

Well to reach those faster speeds requires different input voltages.

You migh consider a fan controller that can handle those fans

LittleBro · 2025-02-11T08:38:39+0000

PWM control will work fine, that's independent of fan size. As for RPMs, this may or may not work properly.
I did similar thing years ago and the reporting results from BIOS were sometimes correct, sometimes badly inaccurate.
Even if you have "same" fans, their RPM will not be the same. Every manufacturer states kind of limits for RPMs (+/- speed % tolerances).
Thus, daisy chaining RPM signal from multiple fans of "same" type will not yield the most accurate results.

Pin for RPM speed does not work as 1-wire bus, fans are not addressable.
To get most accurate results, pick one fan and remove RPM pin connection from others.

System Name	CyberPowerPC ET8070
Processor	Intel Core i5-10400F
Motherboard	Gigabyte B460M DS3H AC-Y1
Memory	2 x Crucial Ballistix 8GB DDR4-3000
Video Card(s)	MSI Nvidia GeForce GTX 1660 Super
Storage	Boot: Intel OPTANE SSD P1600X Series 118GB M.2 PCIE
Display(s)	Dell P2416D (2560 x 1440)
Power Supply	EVGA 500W1 (modified to have two bridge rectifiers)
Software	Windows 11 Home

System Name	PCGOD
Processor	AMD FX 8350@ 5.0GHz
Motherboard	Asus TUF 990FX Sabertooth R2 2901 Bios
Cooling	Scythe Ashura, 2×BitFenix 230mm Spectre Pro LED (Blue,Green), 2x BitFenix 140mm Spectre Pro LED
Memory	16 GB Gskill Ripjaws X 2133 (2400 OC, 10-10-12-20-20, 1T, 1.65V)
Video Card(s)	AMD Radeon 290 Sapphire Vapor-X
Storage	Samsung 840 Pro 256GB, WD Velociraptor 1TB
Display(s)	NEC Multisync LCD 1700V (Display Port Adapter)
Case	AeroCool Xpredator Evil Blue Edition
Audio Device(s)	Creative Labs Sound Blaster ZxR
Power Supply	Seasonic 1250 XM2 Series (XP3)
Mouse	Roccat Kone XTD
Keyboard	Roccat Ryos MK Pro
Software	Windows 7 Pro 64

System Name	CyberPowerPC ET8070
Processor	Intel Core i5-10400F
Motherboard	Gigabyte B460M DS3H AC-Y1
Memory	2 x Crucial Ballistix 8GB DDR4-3000
Video Card(s)	MSI Nvidia GeForce GTX 1660 Super
Storage	Boot: Intel OPTANE SSD P1600X Series 118GB M.2 PCIE
Display(s)	Dell P2416D (2560 x 1440)
Power Supply	EVGA 500W1 (modified to have two bridge rectifiers)
Software	Windows 11 Home

Processor	Intel i5 8400
Motherboard	Asus Prime H370M-Plus/CSM
Cooling	Scythe Big Shuriken & Noctua NF-A15 HS-PWM chromax.black.swap
Memory	8GB Crucial Ballistix Sport LT DDR4-2400
Video Card(s)	ROG-STRIX-GTX1060-O6G-GAMING
Storage	1TB 980 Pro
Display(s)	Samsung UN55KU6300F
Case	Cooler Master MasterCase Pro 3
Power Supply	Super Flower Leadex III 750w
Software	W11 Pro

System Name	CyberPowerPC ET8070
Processor	Intel Core i5-10400F
Motherboard	Gigabyte B460M DS3H AC-Y1
Memory	2 x Crucial Ballistix 8GB DDR4-3000
Video Card(s)	MSI Nvidia GeForce GTX 1660 Super
Storage	Boot: Intel OPTANE SSD P1600X Series 118GB M.2 PCIE
Display(s)	Dell P2416D (2560 x 1440)
Power Supply	EVGA 500W1 (modified to have two bridge rectifiers)
Software	Windows 11 Home

Daisy chaining mixed 4-pin fans

Shrek

eidairaman1

The Exiled Airman

Shrek

nomdeplume

Shrek

Dr. Dro

nomdeplume

eidairaman1

The Exiled Airman

LittleBro

System Name	"Icy Resurrection"
Processor	13th Gen Intel Core i9-13900KS
Motherboard	ASUS ROG Maximus Z790 Apex Encore
Cooling	Noctua NH-D15S upgraded with 2x NF-F12 iPPC-3000 fans and Honeywell PTM7950 TIM
Memory	32 GB G.SKILL Trident Z5 RGB F5-6800J3445G16GX2-TZ5RK @ 7600 MT/s 36-44-44-52-96 1.4V
Video Card(s)	NVIDIA RTX A2000
Storage	500 GB WD Black SN750 SE NVMe SSD + 4 TB WD Red Plus WD40EFPX HDD
Display(s)	55-inch LG G3 OLED
Case	Pichau Mancer CV500 White Edition
Power Supply	EVGA 1300 G2 1.3kW 80+ Gold
Mouse	Microsoft Classic IntelliMouse (2017)
Keyboard	IBM Model M type 1391405
Software	Windows 10 Pro 22H2
Benchmark Scores	I pulled a Qiqi~

System Name	AM4_TimeKiller
Processor	AMD Ryzen 5 5600X @ all-core 4.7 GHz
Motherboard	ASUS ROG Strix B550-E Gaming
Cooling	Arctic Freezer II 420 rev.7 (push-pull)
Memory	G.Skill TridentZ RGB, 2x16 GB DDR4, B-Die, 3800 MHz @ CL14-15-14-29-43 1T, 53.2 ns
Video Card(s)	ASRock Radeon RX 7800 XT Phantom Gaming
Storage	Samsung 990 PRO 1 TB, Kingston KC3000 1 TB, Kingston KC3000 2 TB
Case	Corsair 7000D Airflow
Audio Device(s)	Creative Sound Blaster X-Fi Titanium
Power Supply	Seasonic Prime TX-850
Mouse	Logitech wireless mouse
Keyboard	Logitech wireless keyboard