Disable C1E and make sure in the Control Panel -> Power Options your Minimum processor state is set to 100%. Run Super PI and it should be a constant 26X when 3 cores are disabled in the bios and turbo mode is enabled. The 17.497 number that i7 Turbo reports shows that your multiplier is not at a steady 26 at idle. You need to make those other adjustments until it is steady.