PWM FANS , how do they work and will these work

[bigjonnyauk]

hi guys its been a very very very long time since i built pcs lol the last one i did for myself was a amd 939 i believe

anyways to cut to the chase my son now has a gaming pc which i specced and my cousin built kindly.

but i think we need to put a couple of extra fans in with the summer coming as the temps are ok but could do with a little more air flowing through for the gpu which read 73-78 when gaming.

specs are
phanteks pro m acrylic case
gigabyte z170a gaming 3 mobo
16 gig kingston fury x memory
gigabyte g1 gaming 980ti windforce gpu
i5 skylake 6600k cpu with Cooler Master Hyper 212 Evo CPU Cooler

right my brother has 4 spare akasa 120mm pwm fans which i want to fit and the mobo which can be seen here http://www.gigabyte.com/products/product-page.aspx?pid=5497#ov has 3 sys fans which are 4 pin ones so im prosuming they support this pwm and i have been told i can put the fourth fan in the cpu opt header as long as its the rear fan ?

the three things i need your help on is
1) is the above ok and safe to do
2) how are the fans controlled ? auto ? setting in bios ?
3) my brother seems to think the fans will run at full speed and wont be controlled and therefore will be loud . why would this be ?


thanks guys sorry for long post but its best to give all info in one go

 

[bigjonnyauk]

so for the 70 people that veiwed but never replied or maybe understood themselves then the following might help one of you

so connected all the fans as described and in the bios there was individual settings for each sys fan and the cpu fan and opt .

after a bit of googling it seems i think that the settings of 0.75-2.25 are mulitpliers of the cpu temp so at auto the fans spun at the lowest rpm and highest they spun at max rpm

i set it to manual and gradually increased the multiplier of each one until i got a steady rpm and then from what i gather as the temp of the cpu rises then the fans will increase

ie if the temp is 30 and the multipliers set at 1.5 then the fans will run at 45 per cent

if the temp rises to 45 then the fans will run at 67 per cent

so far it seems to be working ok and temps are down and the gpu temps are down 7-8 degress due to the insides of the case being cooler