Add README with instructions on how to use

Author: veloek

README.md

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+# DisableTurboBoost
+
+A MacOS kernel extension (kext) for disabling CPU turbo boost to keep temperature (and fan noise) down.
+
+## Usage
+
+Since System Integrity Protection (SIP) blocks unsigned kernel extensions, there are a few steps involved in enabling this kext:
+
+1. Reboot Mac into recovery mode by holding down cmd+R when booting
+2. While in recovery mode, open terminal and execute `csrutil enable --without kext`
+3. Reboot back into normal mode
+4. Open a terminal in the folder containing the kext and execute:
+```
+sudo chown -R root:wheel DisableTurboBoost.kext
+sudo chmod -R 0755 DisableTurboBoost.kext
+sudo kextload DisableTurboBoost.kext
+```
+
+Run `kextstat |grep DisableTurboBoost` to verify that it's loaded.
+
+## How it works
+
+This small kernel extension will enable bit 32 of the MSR register `MSR_IA32_PERF_CTL`. This causes the CPU to disable turbo boost, while keeping speed step.
+
+Other similar extensions choose to enable bit 38 of `MSR_IA32_MISC_ENABLE`, but this also disables speed step causing the CPU to run at a higher frequency (and drain battery faster) than necessary.
+
+Take a look in the [manual](http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html) for more info.
+
+## Disclamer
+
+I take no responsibility for whatever harm this kernel extension may cause your system. I use it myself without any issues, but I cannot guarantee it will work for you.
+
+## Troubleshooting
+
+If you get this message when executing `sudo kextload DisableTurboBoost.kext`:
+```
+failed to load - (libkern/kext) not found; check the system/kernel logs for errors or try kextutil(8)
+```
+Try this command in stead: `sudo kextutil -l DisableTurboBoost.kext`
+
+It will output something about invalid signatures, but the extension might still be loaded. Verify with `kextstat |grep DisableTurboBoost`.
+
+## Credits
+
+The code was written by Vegard Løkken with great inspiration from [nanoant/DisableTurboBoost.kext](https://github.com/nanoant/DisableTurboBoost.kext) and [pyrovski/powertools](https://github.com/pyrovski/powertools).