Haswell overclocking basically has two major requirement : A K-series Intel processor & Motherboard with Z87 chipset. However, the third party motherboard manufacturers like Asus,ASRock,Gigabyte & Biostar have exploited the latter requirement, so Haswell overclocking on H81,H87 & B85 chipset is possible using firmware update by the motherboard manufacturers.
Motherboard developers exploited the bug in Management-Engine, a part of firmware that communicates between BIOS & Processor.ASRock was the first MoBo manufacturing company to find a way to send instructions to it which allows the voltage-multiplier to be adjusted in H81,B85 & H87 chipset motherboard.

Hardware.fr folks contacted Intel & Intel replied :

Intel plans to release a microcode update that limits processor core overclocking to Intel Z87 based platforms WW30'13.

This adjustment will be part of the BIOS-Update.So, if once updated, this feature of overclocking will be removed.
So, if you're planning not to upgrade the BIOS, then also the update from within Operating system can patch microcode into the BIOS.

A suggestion : Don't update BIOS & Turn Off the Windows Update, If you wanna enjoy your OC'ed machine in non-Z87 chipset.

Intel is money hungry, they know if the patch won't be released, none of the Z87 chipsets will be sold.

Source : #-Link-Snipped-#