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Disables Turbo Boost Technology on Mac OS X for reliable OpenMP/CL benchmarking

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README.mdown

Turbo Boost Disabler for Mac OS X

This kernel extension DisableTurboBoost.kext lets you disable Intel Turbo Boost Technology present on latest Intel Core processors running Mac OS X.

Abstract

Turbo Boost technology provides automatic CPU over-clocking in certain situations where there is no risk of overheating the CPU. Unfortunately it has nasty effect of ruining various OpenCL and OpenMP benchmark scores.

As observed Turbo Boost triggers when process is occupying 100% of single CPU core, while other CPU cores are idle. However when all CPU cores are occupied, Turbo Boost doesn't trigger as it would cause CPU overheat. As a result parallel tasks performance running on all CPU cores does not scale relatively to number of cores, i.e. for 4 core i5 CPU OpenMP program running on all 4 cores is only ~3x faster than 1 single core version.

Disabling Turbo Boost makes CPU run same clock regardless of cores occupation, therefore we get desired close to 4x speedup when running 4 cores OpenMP program vs 1 core.

This program implements modification of MSR CPU register responsible for Turbo Boost control as described in Table 34-10. MSRs Supported by Intel Processors Based on Intel Microarchitecture Code Name Sandy Bridge (Contd.) - Intel® 64 and IA-32 Architectures Software Developer’s Manual Volume 3C

Prerequisites

Xcode with Command Line Tools is required to compile this module.

Command Line Tools are available as extra add-on from Preferences > Downloads of Xcode 4.3 or newer, installer option on Xcode 4.2 or older or separate download. Separate download does now require Xcode to build this project.

Usage

  1. make
  2. make load to load and disable Turbo Boost (will ask for admin privileges)
  3. make unload to unload and re-enable Turbo Boost (will ask for admin privileges)

License

Copyright (c) 2012 Adam Strzelecki

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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