xnu-speedstep-air is a kernel extension to keep my MacBook from overheating.
It's totally free and works with Mac OS X Maverics (10.9.3). Compare to CoolBook which doesn't since with Lion and costs $10.
It's basically [xnu-speedstep][] with bugfixes and preloaded voltage tables for the MacBook Air Rev. A.
This is updated, and I use it on Macbook Unibody 2008 MacBook5,1 model.
Since Maverics i noticed that the CPU/Voltage goes up very high when using average CPU-Tasks, Eg. Frequency is 1995Mhz and Voltage = 1,1V, but my T9350 (Core 2 Duo) can run it easily in 1995/0.925V. Using AppleIntelCPUPowerManagement.kext it shows even lower in iStats Menu. but as soon as some CPU-Activity is there it goes up to full speed and heats up a lot.
Fortunately, if you reduce the voltage to the processor, the system can run much cooler without thermal protection events happening (like kernel task emitting no-ops or core shutdown).
I was using Coolbook on Snow-Leopard (10.6) but after that it stopped working properly.
HUGE THANKS to [Prashant Vaibhav][msq], [wbyung][], and Superhai for writing this code. I simply made a few changes to get it working on Lion and added voltage overrides for my MacBook Air Rev. A.
You've saved my sanity and tought me a tiny bit about hacking OS X.
This version is now updated for Maverics 10.9. There were some Problems to get it compiled for Target 10.9, but now it works. i had to remove some dependecies and use some older header files, but it compiles in x64 bit. no 32bit involved.
maybe somebody has use for it, even just understanding whats going on with kernel-drivers.
there is no GUI in the moment, but you can change parameters with the Info.plist in XCode or manually edit the Info.plist inside the kext-package.
the voltages are optimized for my MacBook5,1.plist so you have to adjust them.
if you rename the Attribute Info.plist > IOKitPersonalities > IntelEnhancedSpeedStep > PStateTable to Info.plist > IOKitPersonalities > IntelEnhancedSpeedStep > PStateTableOFF
and load the kext it will show the available "vendor" Frequencies and Voltages in console.log (start console.app and filter by "IntelEnh" to find it easily.
A) Workaround For me it does not work together with AppleIntelCPUPowerManagement * .kext so i move them out of /S/L/E/. to a backup-location where i can restore the kext if i need to.
it does work even with APICP.Management in place, but then the Voltage will be reset by the AppleIntel * .kext all the time.
B) Workaround Update, i am now running osx 10.9.5 (dont like the plastic UI in 10.10 so i will not upgrade) I tried it again, as default speedstep in osx uses turbo-boost and jumps Voltage up to 1.1V which really produces heat. i found another tip here: https://discussions.apple.com/thread/4405099?start=15&tstart=0 so if you move the Macbook.plist from /System/Library/Extensions/IOPlatformPluginFamily.kext/Contents/Plugins/ACPI_SMC_PlatformPlugin.kext/Contents/Resources then it will not use speedstep and xnu-speedstep-air can control your cpu. i was lazy and just gziped the plist so i dont have to move it arround, if its zipped osx cannot read it eg. "sudo gzip MacBook5_1.plist" (and "gunzip MacBook5_1.plist.gz" if you want to undo it)
If this Plist is deactivated then also Coolbook works, but only shows your CPU and somehow cannot control the CPU, but its fine to have it as a readout of your CPU Speed and Voltage.
Now my Max CPU is 0.9250V (showing as 0.93V in MenuStats) and stepping down to 0.79V by. also running "yes > /dev/null" (run one for each core, here i run 2 times as i have Core2Duo) so i get 100% CPU . Still Fan keeps slow , temp is low.
I also replaced the paste on the heatsink of CPU and GPU (very tricky assembly on Macbook-Unibody 2008) and now it runs much cooler. Arctic-Silver or similar really works (especially if the old termal paste is 7Years) .
I also use Bootcamp in the moment with Win10-Technical-Preview and overclocking with Nvidia-Tools i can Bump FSB from 266Mhz to Stable 310Mhz, while keeping CPU < 80°C , also GPU can be Overclocked to 500Mhz/1100Mhz (or 530Mhz) in Nvidia-Properties quite stable. In Grid-Autosport it gives an improvement of about 5FPS , going from 28FPS to 34FPS, so i can have stable 30FPS most of the time. Not so perfect but playable. If you have old Hardware and good internet-Connection you can use games.onlive.com where i get solid 60fps in games with high setting in games (locally 30fps in ultra-low) with minimal lag (20ms) over the internet. only drawback is little lag (really not to bad if you get a good server) and some compression due to streaming.
With combination of new Termal Paste, and Xnu-Speedstep i am now idle in 53°C (i Menu stats) or 46°C in Coolbook, and 75°C at both cpu 100% compared to idle 80°C and more on Usage before.
The behavior is similar like you can make Coolbook work with 10.8 or 10.9.
you can watch the current status with (refresh every 10s, or you try --interval=0,1)
shell: watch --interval=10 "sysctl kern | grep kern.cputhrottle"
you can set all the listed parameters of kern.cputhrottle _ * with:
sudo sysctl -w kern.cputhrottle_curfreq=0
to set the first PState. etc.
I kept most stuff like in xnu-speedstep-air, because i was to lazy to rename functions, but it works also on MacBook5,1 and similar Core2Duo (arround 2006 to 2009 Macbooks).
newer models are not supported.
You should understand what this does: if you follow these instructions, you're undervolting your CPU to 892 - 940 mV. I use it on my MacBook Air from 2008 without a problem.
If you're using a different computer, you need to change or remove the PStateTable entry in Info.plist. I only tested it with the MacBook Air Rev. A., computers made after 2008 are very unlikely to work. Failure to be careful may cause hardware instability, crashes, or possibly damage.
Read the LICENSE file. This code is provided AS-IS and at your own risk.
Build the Source using Xcode. You may need to change your build product location (see below).
Run deploy.sh, type your password.
Type: sudo kextload /System/Library/Extensions/IntelEnhancedSpeedStep.kext
Verify it worked: sudo dmesg | grep IntelEnhancedSpeedStep
In Preferences, select the Locations tab.
Click Advanced.
From the dropdown, select: Place build products in locations specified by targets
You'll now get the kext in build/.
it would be possible to create a gui for the sysctl parameters similar to Voodoomonitor _ SLandiCPUSL _ Src
Also check out "MSRDumper" which can show some CPU States, but it crashes easily with kernel-panic if you read the wrong registers.
There is also a PDF of "OSXInternals.pdf" which explains how to build kernel-extensions.
[xnu-speedstep]: http://code.google.com/p/xnu-speedstep/ => now working any more on 10.8+ [psm]: http://paulstamatiou.com/putting-an-end-to-macbook-air-core-shutdown [msq]: http://www.mercurysquad.com/ [wbyung]: http://forums.macrumors.com/showthread.php?t=751657