PWM fan/connectors/air cpu cooler questions

Hi. Let me try to answer your questions:


Older motherboards have 4-pin and 3-pin headers, in which, you can easily determine visually which one is PWM (4-pin) and which one is non-PWM (3-pin). The non-PWM header (3-pin) lacks the 4th pin used for PWM control signal.

Some older and some newer motherboards have all its fan headers with 4 pins - but not all of these headers work electronically the same way - as some are PWM and some are non-PWM. You would have to consult the manual to find out how these 4-pin headers function. 4-pin non-PWM headers have its 4th pin as a "dummy pin" (i.e., no electronic connection).

Most new motherboards today have all its fan headers with 4 pins and with feature to change such 4 pins either in PWM or DC (non-PWM) mode via BIOS -- like the photo link you posted above. Such fan headers are default set in PWM or DC mode out-of-the-box but you can easily configure it whichever mode you like. In the photo, the standard, silent, turbo, and full speed options are just pre-determined curves of the graph to indicate what speed the fan will run on a given temperature. You can set this manually.

Both PWM fans and non-PWM fans can be controlled by the motherboard, if the fan headers of such motherboard have these control features in BIOS. PWM mode has its 2nd pin providing constant +12VDC and, as mentioned above, its 4th pin using PWM signal for variable current communicating with the PWM fan chip to change the fan's speed. On the other hand, DC mode has its 2nd pin providing variable DC voltage (used to change the fan's speed) and, as mentioned above, its 4th pin not electronically connected (dummy pin).

Since both types of fan headers can be controlled in newer motherboards (such as yours), typically, you want to match the fan type with the fan control header mode of the mobo's BIOS. That is, PWM fans = PWM mode; DC fans = DC mode.

Plugging a non-PWM fan on a PWM header will result in the fan running at full speed 24/7 due to the constant +12VDC the 2nd pin provides, i.e., you cannot change the fan's speed. Plugging a PWM fan on a DC header will result in the fan able to change it's speed but through lowering its voltage but the fan is not functioning as a true PWM fan.



That was the case on older (and some new) motherboards (see what I have discussed above).

In the motherboard you ordered, the Asus Z270-A, all of its 6x total fan headers (CPU_FAN, CPU_OPT, CHA_FAN1, CHA_FAN2, AIO_PUMP, and H_AMP) are all 4-pins. All of these fan headers can be changed to work with 4-pin PWM fans and 3-pin non-PWM fans by selecting the appropriate PWM or DC mode as mentioned above.



There are several ways to connect the Deepcool Assassin 2. First is using the Deepcool fan hub as shown in your posted pic. The two CPU cooler fans connect to the hub, then the hub should be connected to the CPU_FAN header (recommended). You can also plug in the hub in a different header (in PWM mode) but make sure you plug something (another fan) on that CPU_FAN header to avoid any error message warning.

Since your motherboard has an abundant supply of fan headers, you can also eliminate the use of the Deepcool fan hub (it's only optional). The fan hub is ideal if you have very limited fan headers or if you just want to save on fan headers for future fan connection/expansion. Since the Asus Z270-A has a CPU_FAN and a CPU_OPT (labelled #3 in the photo link you posted), you can also, optionally, plug one CPU cooler fan on the CPU_FAN and plug the other CPU cooler fan on the CPU_OPT (both headers using PWM-mode).

The above options will function the same way - using PWM signal to control the speed of your CPU cooler's PWM fans based on temperature.

Step 14 just shows an option for mounting the Deepcool fan hub via Zip ties (instead of the 3M sticker in Step 13). The fan hub has a "hole" in the frame body where you can insert the Zip tie to securely fasten the hub in case you don't want to use stickers in your chassis for easier removal later on.



Most motherboards have its fan headers rated at max. 1A, unless otherwise specified. There are some specific headers that can accommodate a higher ampere draw (2A or 3A), such as your Asus Z270-A's H_AMP header (which stands for "high ampere" header).

In connecting several fans running off of one header, you need to check the total ampere draw of all the fans you will use (this is easily seen in the sticker label at the back of the fan or the box or the spec sheet). So, let's say your Arctic F14 PWM draws 0.3A each. Using two of these will total 0.6A - which is still way below the 1A max. on typical motherboard fan headers -- you'll be safe. However, plugging another 0.3A fan will total to 0.9A -- a bit close to the max and not recommended. You can use a lower amp fan though (like 0.15A) to add to your 0.6A total. So, the point is, compute the total amount of draw so as not to reach the limit.

If you have high amp draw fans, you can safely use the H_AMP header in your motherboard to connect all those fans (after computing the total draw) via a fan hub. You can set the mode in PWM if you are using PWM fans.

Alternatively, connecting such fans to the PSU (via a 4-pin to molex cable) is also doable. However, you'll be running the fans at full speed 24/7 and lose the fans' PWM function if they are PWM fans.



The Corsair AF140L and AF120L case fans are both low-speed 3-pin DC fans. The AF140L is 140mm in size, while the AF120L is 120mm in size.



No you can't. It will run full speed 100% 24/7 without any control (similar to connecting a 3-pin DC fan in a 4-pin header in PWM-mode, as I mentioned above).



That's the logical airflow:
Front (and Bottom, if any) = Intake
Rear (and Top, if any) = Exhaust

But, it's all a matter of preference really and a case-to-case basis. It's not a pre-determined orientation and you can choose which direction you mount your fans if it will help lower the particular temperature in your chassis.

raisonjohn's advice and info above is excellent. Follow it.

Just FYI about your question 1a on multiple options. The "normal" way to set the options for EACH fan port is to use the "Standard" mode. This uses a pre-set group of settings for fan speed versus actual measure temperature that is very well suited to most needs. But some people prefer to change from that, so others are offered here. "Silent" forces the fan to run slower than normal, which MAY mean your system is running hotter that "ideal", and certainly will mean it will never use the fan's full speed and cooling ability. "Turbo" is the opposite - the fan runs faster than normal, making more noise and providing cooler operation than "Standard". "Full Speeds" means the fan is NOT under any automatic control based on temperature, it just runs full speed all the time. "Manual" allows you to take the bending points on the graph above and change them interactively to set your own custom version of what the automatic system will do for this fan.

Note that EACH fan header can be configured separately. If you want to make changes, do changes for every fan header - what you do on one will NOT be automatically applied to any others.

The manual says the mobo actually contains more than one temperature sensor that can be used to guide automatic temperature-based control of fan speeds, but does not show how to choose those.

Background: every automatic fan speed control system is really a TEMPERATURE control system. That is, the AIM of each is to control the TEMPERATURE as measured by a sensor. The system manipulates the speed of a fan to do this. On most mobos there are two separate such control systems. The CPU_FAN header always is based on a temperature sensor built into the CPU chip itself and available to the mobo as a signal on one of the chip's pins. Normally any CPU_OPT header also is based solely on this sensor. Most mobos apply extra monitoring of the performance of the actual CPU cooler to ensure the CPU chip can never overheat and be damaged, BUT they do this in part by checking the speed signal of the fan plugged into the CPU_FAN header. So it is IMPORTANT that the actual CPU cooling fan be plugged into the CPU_FAN header.

The second "normal" control system is used for the CHA_FAN headers and uses a sensor built into the mobo. This normally is used for case ventilation fans. Your mobo has two of those headers, plus some others. It also has much more flexibility than many mobos. The result is that you can make separate configuration choices for each fan header to customize what their fans do. For each you can choose which temperature sensor is used (and how/where? is what I cannot find in the manual), whether it uses PWM Mode (for 4-pin fans) or DC Mode (for 3-pin fans) as a control method, and the fan Profile (i.e., which of those several options for speed versus temperature). For all your case fans I suggest you start with using the Motherboard temperature sensor, the "Standard" profile, and set the control Mode to PWM or DC according to the fan type you plug into that header. IF you choose to use a splitter to connect two or more fans to one header, be sure to connect together ONLY fans of the same type (3-pin together, and 4-pin together) and set their header accordingly.

In my view, the Deepcool "Fan Hub" included with that cooler system is really a Splitter, but it will do what you need very well. Picky of me, maybe. I use the term "Splitter" to label a device that simply connects two or more fans in parallel to a single header and thus provides power and control of all its fans solely from that header. This works just fine if the total fan load on the header is less than 1 amp for most headers, and that is what your Deepcool Assassin II system will do nicely for your CPU_FAN header. To me, a "Hub" is a different device that gets power for its fans directly from the PSU using a separate connection cable, and thus avoids the 1 amp limit of a normal header. Such devices normally can work only with true 4-pin headers that use PWM Mode, and with 4-pin fans only. But you have so many mobo fan headers, each with very flexible configuration options, that you don't need such a device.