Proprietary Intel Driver for Processor Microcode Firmware Seems to Disable Overclocking

I installed Ubuntu 14.04 on Asus B85M-G motherboard with G3258 CPU. This CPU has good overclocking possibilities and I was able to overclock it without hassle. Due to minor issues with hibernation and graphics, I upgraded to 15.04 and turned on “Intel proprietary driver for processor microcode” - then overclocking possibility was gone. After turning this driver off, overclocking was possible again. I am wondering whether it is deliberate action (as suggested, for instance here: ) or just some additional configuration is needed.