This kernel extension
DisableTurboBoost.kext lets you disable Intel Turbo Boost Technology present on latest Intel Core processors running Mac OS X.
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
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.
make loadto load and disable Turbo Boost (will ask for admin privileges)
make unloadto unload and re-enable Turbo Boost (will ask for admin privileges)
Copyright (c) 2012 Adam Strzelecki
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