Solution
BFG-9000
Splendid
- Sep 17, 2016
- 3,843
- 636
- 29,590
All you have to do is look up the amps the header is good for, and add up the amp rating of both fans to know if this is OK
CountMike
Titan
- Oct 31, 2015
- 34,973
- 3,587
- 147,990
Usual power output capacity of MB headers is 1A at 12v, It takes 3-4 normal 120-140mm fans. For PWM fans it's fairly important to be same and for splitter to have 4pins on one branch and 3 pins (RPM sensor missing) on other branch.
eziowar asked, "ty, btw why this is needed - ". Here are details.
All fans generate a speed signal consisting of 5VDC pulses (2 per revolution) sent back to the host header on Pin #3. The header counts those to calculate speed. It displays the result but does NOT use it for speed control. However, it DOES monitor that for NO pulses or very LOW speed result which indicates fan FAILURE. If that happens, you get a prominent warning in your screen. For the CPU_FAN header (and some related ones) the action will be more drastic. Within a short time of failure detection, the system may be shut down completely without waiting for the temp sensor inside the CPU chip to detect a high temperature. This is to prevent rapid overheating of the CPU when there is NO cooling, resulting in permanent damage. Such CPU_FAN headers also may NOT allow you to boot up at all if it does not get a valid speed signal at the CPU_FAN header immediately when the boot process starts.
The header counts those pulses coming in. IF one were to connect to that Pin #3 of the header the pulse signals of two or more fans, the composite pattern would have very erratic timing with many more pulses than it should have. The header cannot get a correct count on that, and the result fluctuates wildly to generate errors. The solution is simple. When you use either a Splitter or a Hub to connect more than one fan to a single header, the Splitter or Hub will send back to the host header the speed from only ONE of its fans, and ignore all the others. The speeds of the "others" are sent nowhere, and will never be "seen". This has NO impact on ability to control the fan speeds, but it does mean that the header can NOT detect failure of most of the fans there. So from time to time YOU should look and verify that all fans still are working.
For a Splitter or Hub that looks like a collection of cable "arms" only ONE male output connector will have all 4 pins. All others are missing Pin #3 so they can NOT pass their fan's speed signal back. For a unit that looks like a circuit board or for one that looks like a closed box with male ports recessed inside holes, similarly only ONE output port will feed its fan's speed signal back to the host header. In these cases that one port will be marked in some way. SOME units will mark that for use with the CPU fan, but you do NOT need to connect the real CPU cooler unit to this port. You do that ONLY if the unit is connected to the CPU_FAN header and your actual CPU cooler is to be connected to the Splitter or Hub. If that unit is being used only for case ventilation fans then ensure that ONE fan is plugged into the marked output port so a speed signal IS sent to the header.
Remember that you CAN use 4-pin Splitters or Hubs with BOTH 3-pin and 4-pin fans. Almost all on the market are like this now, with few 3-pin units available. The fact that a male output connector has Pin #3 of its 4 pins missing does NOT have anything to do with 3-pin or 4-pin fans. The missing pin impacts ONLY what happens to the speed signal.
All fans generate a speed signal consisting of 5VDC pulses (2 per revolution) sent back to the host header on Pin #3. The header counts those to calculate speed. It displays the result but does NOT use it for speed control. However, it DOES monitor that for NO pulses or very LOW speed result which indicates fan FAILURE. If that happens, you get a prominent warning in your screen. For the CPU_FAN header (and some related ones) the action will be more drastic. Within a short time of failure detection, the system may be shut down completely without waiting for the temp sensor inside the CPU chip to detect a high temperature. This is to prevent rapid overheating of the CPU when there is NO cooling, resulting in permanent damage. Such CPU_FAN headers also may NOT allow you to boot up at all if it does not get a valid speed signal at the CPU_FAN header immediately when the boot process starts.
The header counts those pulses coming in. IF one were to connect to that Pin #3 of the header the pulse signals of two or more fans, the composite pattern would have very erratic timing with many more pulses than it should have. The header cannot get a correct count on that, and the result fluctuates wildly to generate errors. The solution is simple. When you use either a Splitter or a Hub to connect more than one fan to a single header, the Splitter or Hub will send back to the host header the speed from only ONE of its fans, and ignore all the others. The speeds of the "others" are sent nowhere, and will never be "seen". This has NO impact on ability to control the fan speeds, but it does mean that the header can NOT detect failure of most of the fans there. So from time to time YOU should look and verify that all fans still are working.
For a Splitter or Hub that looks like a collection of cable "arms" only ONE male output connector will have all 4 pins. All others are missing Pin #3 so they can NOT pass their fan's speed signal back. For a unit that looks like a circuit board or for one that looks like a closed box with male ports recessed inside holes, similarly only ONE output port will feed its fan's speed signal back to the host header. In these cases that one port will be marked in some way. SOME units will mark that for use with the CPU fan, but you do NOT need to connect the real CPU cooler unit to this port. You do that ONLY if the unit is connected to the CPU_FAN header and your actual CPU cooler is to be connected to the Splitter or Hub. If that unit is being used only for case ventilation fans then ensure that ONE fan is plugged into the marked output port so a speed signal IS sent to the header.
Remember that you CAN use 4-pin Splitters or Hubs with BOTH 3-pin and 4-pin fans. Almost all on the market are like this now, with few 3-pin units available. The fact that a male output connector has Pin #3 of its 4 pins missing does NOT have anything to do with 3-pin or 4-pin fans. The missing pin impacts ONLY what happens to the speed signal.
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