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Question Fan hub that works with 3-pin and 4-pin fans and 4-pin board

HerrKaLeu

Member
Nov 23, 2016
100
5
81
I have a board with 4-pin chassis fan connector. It is able to run my 3-pin case fans and modulate the speed. Now I want to control all 4 case fans over that connector and think using an active fan hub is better to not overload the connector. What I do also should work for future boards.

I'm aware of the 3/4 pin issue and many of the hubs claim the 3-pin fan will just run full speed. I'm not planning to replace my expensive 3-pin fans, so need a hub that also will run the 3-pin fans at regulated speed.

I found this Phantek PH-PWHUB-02 ($24) that sounds like it will do what i want (run 3-speed fans at lower speed on my 4-pin mobo). Is that correct?

Any other suggestions? I know newer cases come with these hubs built-in, but I plan to keep this case.
 

Paperdoc

Golden Member
Aug 17, 2006
1,952
128
106
Yes, that Hub WILL do what you want. In fact, it is one of VERY few that can. It actually has four ports that run truly under the old Voltage Cotnrol Mode for 3-pin fnas, and four others that run in the new PWM Mode for 4-pin fans. Like all Hubs, it REQUIRES that its mobo host header be using the PWM Mode. There is one small detail I am not sure about. Like all Hubs, it will return to its host header the speed of only ONE of its fans. I believe that is only the one on the first 4-pin fan port, so that if you have only 3-pin fans on their ports it may NOT return any speed signal to the host header. IF that happens and causes your mobo to issue warnings of fan failure on that mobo fan header, you may need to try to tell it to Ignore that speed signal, or to not send any error messages.
 

HerrKaLeu

Member
Nov 23, 2016
100
5
81
Thanks for the response. Yes it took me some searching to come up with a suitable hub. I'm puzzled by the fact that most hubs don't actually control the 3-pin fans. If I wanted to run the fan at 12V, i could just power them directly from a Molex/SATA cable.

I ordered it and will report how it goes. The connector will be omnone of the 2 chassis fan connectors on the mobo, so I assume the Mobo won't care if it thinks the case fan doesn't work. The CPU fan will run from the actual CPU connectors.
 

Paperdoc

Golden Member
Aug 17, 2006
1,952
128
106
The vast majority of fan Hubs are designed solely to work in 4-pin fan systems. They use 4-pin outputs. They distribute to those the Grounds and +12 VDC power supply lines they get from the PSU.Then they also distribute to all their outputs the PWM signal (on Pin #4) they get from the mobo host header. In this way ALL of the Hub outputs become exact duplicates of the standard 4-pin mobo fan header operating in PWM Mode, except that they are not so limited in total electrical load.

The design of the new 4-pin PWM fan system included as much "backwards compatibility" with the older 3-pin system as they could. Minimal changes to physical layout and electrical function of the pins achieved some of this. One result is that, if you plug a 3-pin fan into a new 4-pin header using PWM Mode, the fan receives a constant full 12 VDC and Ground power supply from Pins 2 and 1, and can return its speed signal on Pin #3. Since the voltage from Pin #2 never is reduced (as it would be in the older 3-pin header system), the fan can only run full speed all the time. This has the advantage that the old fan DOES work - in fact, maybe too much, but that is better than reduced. The makers of Hubs simply have disguised this factor by saying their hubs are "compatible with 3-pin fans". The do not always make clear that this means no speed control.

All mobos do careful monitoring of the speed signal of the "fan" connected to the CPU_FAN header. If that fails (in some cases, if it falls below a minimum you can set), at minimum the BIOS will pop up a prominent warning on your screen to alert you. Many mobos also wait only a short time before the simply shut down the system to prevent CPU overheating and damage, even without ever waiting for the temp sensor inside the CPU to detect rising temperatures. On case ventilation fan headers, most also monitor for fan failure. But their actions thereafter normally are limited to posting the warning, and relying on you to take appropriate action. In both cases, may mobos offer you a configuration option to Ignore the fan speed item, which means both that it will NOT be measured and dsiplayed, and that it will NOT be monitored for failure.
 

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