Kingston makes HyperX Plug-n-Play 1600MHz DDR3 RAM with "automatic" overclock SPD settings that are supposed to be read by your BIOS and thus your memory controller. They also come in 1866MHz speeds. Corsair makes the same stuff with slightly better (faster) timings than the Kingston in their Vengeance line for notebooks (e.g.
http://www.corsair.com/memory-by-product-family/vengeance/vengeance-8gb-high-performance-sodimm-memo... again with "plug-n-Play" automatic overclocking of the memory controller to 1600 or 1866MHz. You have no choice but to try this "PnP" stuff as the G74 BIOS has no functionality to manually overclock the IMC to the rated speed of the RAM you stick in it, mores the pity.
In the G74 it has been observed that 2x4GB=8GB of the 1866MHz Kingston stuff works at full speed, while filling all four banks with it (for 16GB) causes the memory controller to "downclock" to stock 1333 MHz speeds. We suspect its a BIOS problem with the G74. However, folks around here have gotten 4x4GB=16GB of the 1600 MHz stuff to work fine in the G74.
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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