Have never used a G73, so not sure about what a turbo button is. In the G74 Turbo is handled by Intel's Turbo Boost, which automatically overclocks the cpu freq. according to the workload (from 1--all 8 threads) and the chip's heat output and "thermal distance" to its Thermal Design Power (similar to total dissipated power, in watts). The core i7 2630QM (stock=2.0GHz) for e.g. can OC anywhere from 2.5 GHz to 2.9 GHz (max),though for some reason the G74 running Windows 7 slightly cripples the max CPU clock to 2.7-2.8GHz.
You don't need to turn on Turbo Boost: its is enabled by default. A good BIOS (none are available for the G74) will allow you to turn it on/off though.
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G74SX-CST1-CBIL, i7 2630QM 2GHz
32GB DDR3 RAM @1333MHz
GTX560M 3GB DDR5 (192 bit)
17.3" LED 1920x1080
Sentelic TP, BIOS 203
Debian Linux Wheezy (Testing) Kernel 3.2, NVIDIA 295.40