have done this and i get to 3.6ghz every few seconds but it is fluctuating from 33-36 multiplier which is causing the cpu to jump every few seconds between 3.3ghz, 3.4ghz, 3.5ghz and 3.6ghz in a random order.
I use to have locked Intel Xeon Ivy Bridge processor tried using a similar setting on a Z77 MSI motherboard, and observed the same behavior with clock speed fluctuating even when the processor was idle. Simply the Xeon was hard locked you were not allowed to adjust the multiplier.
What your witnessing is Intel's Turbo Boost kicking in for 2 cores with a light load (max turbo frequency), medium load it will drop down a multiplier, and for a heavy all cores loaded it drops down to processor base frequency.
On my 4790K at default settings it's processor base frequency set by Intel is 4.00 GHz but with a heavy load it actually runs at 4.2 GHz with all cores loaded the same should apply to your i5-6500. Try using CPU-Z to monitor the clock speed with a load over all cores it should be running slightly above the processor base frequency.
Time for the bad news, since you have a locked processor Intel removed the option starting with Haswell
allowing you to force the Turbo Boost frequency over all cores so the Asus Multi Core Enhancement no longer functions on a locked processor unless you have a 6600K or the 6700K.
Found an old thread in the forums:Overclocking non-K Intel CPUs? - The Techreport Forums
News post from the front page:Intel removes modest 'free' overclocking from standard Haswell CPUs