Consider from this point of view. All of these fans are actually under the control of loops that concentrate on the measured TEMPERATURE at specific sensors in the system. Further, they all assume that the general CASE vent fans will do their thing guided by the temperature measured by a sensor on the MOBO, and that establishes the temp of the air available for use to cool the CPU and GPU chips. So those latter two systems do NOT expect to have outside air as their source. The CPU cooler (especially the type you have, a fan and heatsink on the CPU chip) uses a temp sensor inside the CPU chip and adjusts is fan speed to keep that where it is supposed to be. NOTE that, if you were to provide cooler air to that fan for this purpose, the fan control system would simply find that the CPU is running cooler than planned, and slow the fan down a bit to keep the CPU temp on target - it may NOT actually decrease the CPU internal temp! Similarly, for the GPU chip, it has its own control system based on the real GPU internal temp, and using the normal case interior air.
There is another factor - the availability of data. Usually the CPU_FAN header will ONLY allow the use of the sensor inside the CPU chip. SYS_FAN or CHA_FAN headers on the mobo normally are set to use the mobo sensor - actually, a sensor in a spot the mobo maker judges the most important for cooling of all major mobo heat sources. Often there is an option for some of these headers to use other sensors instead - either the one inside the CPU, or others on specific mobo components. These are really suitable for use IF you are creating a special cooling loop for a particular component by dedicating (by aiming) a fan at that item, and the using its own sensor to guide that one fan. But using the CPU temp to guide mobo cooling generally is not so good.
The GPU fan is a very different matter normally. There has never been a standard means of sending the temp measurement inside the GPU chip out to the mobo, so NO system has the MOBO controlling cooling of the GPU chip. Instead, the video card itself has its own fan control system guided by that GPU internal sensor, and expecting to use general case air. So normally you can NOT control GPU cooling using a mobo fan header, and you cannot feed any mobo or CPU temp sensor info into the video card to guide its fans. In almost all cases you will find that control and configuration of GPU chip cooling is done using utilities supplied by the video card maker that communicate with that card, and not with the mobo.
If you really believe that you need your mobo or CPU temps to run lower, on most mobos you have the option to set your own version of a "fan curve" for each header. That is the settings of what fan speed to run for a given temp measurement. You can set it to run faster at all temps and force it to run your components cooler under most conditions. There may be a limit that, at max workload and heat generation, you find the fans already have been set to run full speed at a lower temp and you've reached the fan cooling limit, but that is not usually a big concern. Doing this will cause marginally faster fan wear. Whether or not it also results in longer lifetime for the units you over-cool this way is very hard to say.
Facebook
Twitter