Limiting the MAX fan speed on the MBA via smcFanControl

Scott6666

macrumors 65816
Original poster
Feb 2, 2008
1,337
481
I saw an interesting post today by pgharavi who says he is using SMCFanControl to set the max speed of his fan to 4000RPM:


From the terminal:
/Applications/smcFanControl.app/Contents/Resources/smc -k F0Mx -w 60e0

(that's the default 6200 RPM)

/Applications/smcFanControl.app/Contents/Resources/smc -k F0Mx -w 3e80

(That's 4000 RPM Max)

I obviously gain a few degrees C when limiting to 4000, but at least my MBA shuts up.
Not to question his knowledge but have others tried this and does it really work?

I might not go so far as to set the fan to 4000 (but I might). Given all the thoughts on Coolbook, what do you all know/think about this? Safe and effective relief from fan headaches?
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
https://forums.macrumors.com/posts/5266108/

I thought about making a thread but I've been too busy. I would suggest changing the topic title to something akin "Limiting the MAX fan speed on the MBA" to get more attention to the specific issue.

Anyway, the app, by itself, will NOT keep your MBA quiet. The GUI purposely doesn't allow you to do this (see the FAQ).

Like I said in the previous topic, you can also increase the max fan speed using terminal.

Thanks for making the topic.
 

netddos

macrumors regular
Oct 22, 2005
128
0
how do we write a script that runs this command during startup and after waking up from sleep?
 

sir. mac

macrumors regular
Nov 21, 2006
113
0
how do we write a script that runs this command during startup and after waking up from sleep?

I thought this was a hack for SMCFanControl, meaning that whenever it runs (as on startup) this fan-limiting script will be active? I haven´t tried it yet, so sorry if this is an embarrassing assumption :)
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
I thoiught this was a hack for SMCFanControl, meaning that whenever it runs (as on startup) this fan-limiting script will be active? I haven´t tried it yet, so sorry if this is an embarrassing assumption :)
I actually don't have the app running at all. It's not necessary for the terminal command.
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
That means that you will have to reapply the script in terminal after reboot and wake froom sleep?
I made a script and instructed the MBA to run it after boot. I wanted to upload it here but the forum won't let me. It's a simple automator script that auto runs at boot and then closes itself.

If I watch a movie, I just open terminal and enter in the full speed command.
 

netddos

macrumors regular
Oct 22, 2005
128
0
I made a script and instructed the MBA to run it after boot. I wanted to upload it here but the forum won't let me. It's a simple automator script that auto runs at boot and then closes itself.

If I watch a movie, I just open terminal and enter in the full speed command.
do you mind giving us the script for us?

i'm new to mac and have no idea how to run the script automatically..

it isn't like windows where you can just put .bat file under "startup" folder..
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
do you mind giving us the script for us?

i'm new to mac and have no idea how to run the script automatically..

it isn't like windows where you can just put .bat file under "startup" folder..
I didn't know either until like 2 days ago ;)

Just go to Automator, choose custom, and then find terminal or whatever. Then paste in the command from the OP (for 4000 RPM). Then save it as an app, and then put it anywhere you want (I leave mine in Docs).

The final step is to go to your system pref., and then Accounts, Login Items, and then add your little app you just made.
 

stakis

macrumors member
Oct 25, 2007
94
0
I didn't know either until like 2 days ago ;)

Just go to Automator, choose custom, and then find terminal or whatever. Then paste in the command from the OP (for 4000 RPM). Then save it as an app, and then put it anywhere you want (I leave mine in Docs).

The final step is to go to your system pref., and then Accounts, Login Items, and then add your little app you just made.
hey where in the automator list can you find Terminal... I can't find it anywhere...

thanks
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
hey where in the automator list can you find Terminal... I can't find it anywhere...

thanks
Custom > Utilities > Run Shell Script

That's where you paste the command. Delete the 'cat' text in there first.

:)
 

msinco

macrumors newbie
Dec 14, 2007
18
0
Thanks

Thanks on the tip regarding the fan control as well as the automator tip.
After purchasing coolbook, this is exactly what i need.

Instead of putting the automator app at login, i created an automator app that drops the fan to 4000rpm, waits for 10 seconds and returns the setting to default 6200rpm. Im still afraid to set it at 4000rpm all the time. I just need this to tell the macbook air to shut up for awhile. Once it hits 4000 rpm, it usually doesnt go back up and just hovers around 4500rpm.. which is good enough for me.
 

stakis

macrumors member
Oct 25, 2007
94
0
Thanks on the tip regarding the fan control as well as the automator tip.
After purchasing coolbook, this is exactly what i need.

Instead of putting the automator app at login, i created an automator app that drops the fan to 4000rpm, waits for 10 seconds and returns the setting to default 6200rpm. Im still afraid to set it at 4000rpm all the time. I just need this to tell the macbook air to shut up for awhile. Once it hits 4000 rpm, it usually doesnt go back up and just hovers around 4500rpm.. which is good enough for me.

What a chicken!!!!!

nah , just kidding.... whatever makes you feel comfortable! but don't you notice that when at 6200rpm the CPU is running in the low to mid 60 degrees?? I don't understand this.
 

juro

macrumors member
Nov 11, 2007
97
0
Don't you guys think that limiting the fan speed is just plain asking for trouble?

The fan is running at that speed to cool the machine off. Sacrificing cooling just to quiet the machine down might toast it.
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
Don't you guys think that limiting the fan speed is just plain asking for trouble?

The fan is running at that speed to cool the machine off. Sacrificing cooling just to quiet the machine down might toast it.
No, it's fine. Like I said, if you are doing wireless productivity, the gain is usually only 1-3 C. Nothing.

Even watching videos the gain is 5 C max. But for that, I would, and do, put the fan back up to 6200.
 

MayaTlab

macrumors member
Dec 12, 2007
87
16
Hi, I would like to know if I can set the fan up so that they won't rotate over 2500 rpm and not just 4000 rpm. Is it possible ? It seems the command line for 4000 rpm is "3e80". Should I write "2e50" ?

I ask this question because I am very sensitive to noise and really bothered, even at 4000 rpm. And since I have changed the thermal paste and use coolbook I intend to limit the maximum temp at 80 degrees (even if it means that the processor would have to slow down, because the stuff I do on my MBA is not processor intensive).

Thank you for your answer !
 

1appleAday

macrumors regular
Mar 27, 2008
195
0
Hi, I would like to know if I can set the fan up so that they won't rotate over 2500 rpm and not just 4000 rpm. Is it possible ? It seems the command line for 4000 rpm is "3e80". Should I write "2e50" ?

I ask this question because I am very sensitive to noise and really bothered, even at 4000 rpm. And since I have changed the thermal paste and use coolbook I intend to limit the maximum temp at 80 degrees (even if it means that the processor would have to slow down, because the stuff I do on my MBA is not processor intensive).

Thank you for your answer !
So after you reapply thermal paste and use coolbook, the fan speed still high? mind to share the temp and fan speed after you did both? I'm also bothered by fan noise, but if using coolbook and reapply thermal paste (as in your case) still won't make the Air quiet, i may as well give up and live with it. Thanks!
 

MayaTlab

macrumors member
Dec 12, 2007
87
16
Actually it depends on your usage. You might feel fine if running CPU-only intensive tasks since the fan only turns on when the CPU go over 70 degrees or the heatsink 55 degrees (at least on mine).

Though, if you plan running graphic average intensive tasks (such as a MP4 file), then the fans will turn on quickier because you will be using the integrated chip for Core Image, thus resulting in a superior increase of the heatsink (and not CPU) temp.

This is why I am now able to encode a DVD with Handbrake with very little fan noise but unable to watch the resulting MP4 file without the fans rotating over 4500 rpm !

EDIT : In addition to my previous question, do I have to install SMC fan control even if running the app itself is not necessary ?
 

pgharavi

macrumors 6502
Nov 25, 2004
255
194
EDIT : In addition to my previous question, do I have to install SMC fan control even if running the app itself is not necessary ?
I think so. Notice the command references the application. As per your earlier Q, I don't know. there is command (I think it' -h) that will tell you the command for all the...commands...lol)
 

1appleAday

macrumors regular
Mar 27, 2008
195
0
Hi, I would like to know if I can set the fan up so that they won't rotate over 2500 rpm and not just 4000 rpm. Is it possible ? It seems the command line for 4000 rpm is "3e80". Should I write "2e50" ?

I ask this question because I am very sensitive to noise and really bothered, even at 4000 rpm. And since I have changed the thermal paste and use coolbook I intend to limit the maximum temp at 80 degrees (even if it means that the processor would have to slow down, because the stuff I do on my MBA is not processor intensive).

Thank you for your answer !
Did you try limiting the fan speed to 2500 Maya? What's the max temp you've seen after limiting the fan to such low speed?
 

MayaTlab

macrumors member
Dec 12, 2007
87
16
Well, I have not been able to determine the hexa code for 2500 so I am currently at 4000 rpm, encoding a DVD with Handbrake. The CPU temp is 76 degrees and the Heatsink 63 degrees. I use CoolBook to throttle down the CPU to keep the temp under 75 degrees, so now my CPU is at 800 mhz, which is fine for me : why would I need handbrake to be faster if I encode during the night ? Moreover, with the fan set at 4000 rpm I can sleep while encoding :).
 
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