27 iMac individual fanspeeds - SMC FC

[powerhouse7]

Hi,
I'm a little worried with my temperatures for my i7 Imac. Its not so much the CPU that worries me, it doesn't go above 50 degrees celsius. Its the GPU.
When using normal fan speeds it idles at 60. I know this isn't problematic but I want it to idle around 50, so i've been using SMC Fan Control to do so and have had no problems.
What i'm also worried about however is burning out my fans.

So, my question is: Of the three fans in the iMac (entitled by SMCFC as ODD, HDD, and CPU) regulates best the temperature of the GPU so I can just increase this fan and not the others.
I'm pretty sure the answer is ODD (optical drive?) because if i've got the acronym right then that's where the gpu is located (generally) as well.
But I want to be sure on this, because this will be a long term fix.
I really appreciate any input.
Thanks for your time.
Powerhouse

 

[spinnerlys]

Thus it seems, the ODD fan is nearest to the GPU.

iFixIt TearDown of the 27" iMac

 

[peakchua]

2000 rpm cpu and 2700rpm hdd the odd will spin faster when the hdd and cpu does but odd 2300 rpm (set) my istatpro said it spun without setting it at 3500 rpm. since the db is realy quiet you can put it like that compared to the 20 inch imac since the fans are loud. i put mine at 1600-1800 rpm it just spread more heat evenly

 

[powerhouse7]

Thanks so much!
I don't want to put my fan speeds up too much. So i've decided to try out increasing just the ODD fromm 1000 to 1500 rpm and see what kind of different it makes. Already, after 30 seconds of use the heat of the GPU is down to 53 from 60. So it seems to be working.
Thanks again.

 

[aki]

Seems like you have already addressed your issue but just wanted to point out (which you probably know already) that the three fans are designed to work in concert help to lower temperatures overall; and so you may find that increasing each fan slightly ends up working as well as increasing just the one closest to the component you are concerned about. (In the iMac, I'd worry more about the HD than the GPU, anyway.) Then again I'm not an engineer so what would I know .

Also, you don't have to be toooo paranoid about fan lifespan. The aren't especially fragile components and are simple/cheap to replace (compared to a GPU).

 

[peakchua]

to me the fan speeds inside the imac on default are stupid. all the fan speeds inside make th e heat spreppd around and but no airpractically comes out like when i try to feel the air of 1200 rpm cpu it doesent work. when i rev it up to 1600 (my room is cold) it is slightly better. my imac now stays at 29 degrees and im ina hot country....

 

[peakchua]

Thus it seems, the ODD fan is nearest to the GPU.

iFixIt TearDown of the 27" iMac

? i thought the gpu was the one on the bottom right

 

[TMRaven]

The gpu is on the right side of the iMac when it's facing you, so his picture is right.

The cpu of a computer will always be somewhere on the motherboard, while a dedicated gpu is usually has its own daughterboard and connected through some sort of pin interface-- in this case it's an mxm interface (mobile pci express)

The optical drive fan is directly below the gpu's heatsink, so in this case the odd fan will provide the best solution to cooling the gpu.

 

[peakchua]

i like imac fan control.. you should set your threshold at 40 celcius and the other one on the equiivilant.. then set your fan (all of them) at 1600 rpm 2700 rpm and let the odd do its job the odd will not spin faster even if you set it