i need a 140mm front fan and a 120mm rear fan but have got confused looking at them all as to what type i need? I want as quiet as possible for the fans and cooler.
If you are plugging the fans into your motherboard, you want fans with a 4 pin connector. What they call "PWM" fans. These use "
Pulse
Width
Modulation" to automatically adjust fan speeds based on temperature readings from the motherboard and CPU. There will be fan headers on your motherboard that read things like "CPU1" or "CPU2" which is where you would plug in the fans for the CPU cooler and "SYS1" or "SYS2" or others for where you would plug in the fans for the case.
The other type of fan uses a 3 pin connector. These DO NOT feature PWM (because they lack the 4th line / connection of a PWM fan) and will only ever run at full speed if plugged into a motherboard. They can however, be manually adjusted by using a dedicated fan controller.
For example I recently replaced 2x140mm and 1x120mm PWM Noctua fans from my case with all 120mm 3 pin fans which are connected to a dedicated fan controller.
These were the 140mm fans.
This was the 120mm fan. Those were plugged directly into the motherboard. They were great fans, but I needed to run fans at full speed in my server box, so replaced them all for 3x120mm 3 pin fans I salvaged from some old Noctua AMD Opteron heatsinks and those are connected to a dedicated fan controller that I can manually adjust to set all the fan speeds to high and exhaust more air. The only problem with that is faster / more RPM = more noise. The PWM fans adjusted automatically, ran slower, but didn't push as much air.
In a desktop machine that might not be too important, but in a server with a 130watt chip I need to get as much air out of the machine as possible.
The cpu cooler would need to fit my rubbish msi-h61m-p31 board and not block the gpu or ram.
That motherboard is a socket 1155 board. So you want to look for heatsinks / coolers that list as being 1155 compatible. That will fit your socket. But more important than that is you want to find a heatsink / cooler that will clear your RAM and not be so HUGE it sticks out the side of your case, then you end up you can't get the side panel back on. An example being
this Noctua cooler. If you look at the product description details you can see socket compatibility (LGA1155 is listed which means it will fit your socket).
Then it's just a matter of finding a heatsink / cooler within your budget. The example I linked uses 120mm fans and for the most part should fit in most cases without issue (and should clear most RAM / GPUs). They also make coolers that use 140 and 150mm fans. This is where you really start running into fit problems and need to check and double check if the cooler will fit and clear your RAM / GPU. They also make coolers with smaller fans, but as size decreases in fans, I've found they tend to run much higher RPM to push the same amount of air and like I mentioned before about the case fans faster / more RPM = more noise.
Hope some of that helps
