That so called Vcore reading in Z87 ASRock boards is the CPU input voltage, not a CPU core voltage, as others have said in this thread. My ASR Z87 EX 6 board displayed 1.8V for "Vcore" in the UEFI and A-Tuning, which is just plain wrong.
As others have said, CPU-Z 1.64.2 will show the correct CPU core voltage, as well as the current HWiNFO64 Beta (1945), and the latest AIDA64 Beta is correct too.
Actually, each CPU core has its own core voltage reading, so displaying only one core voltage does not really show was is happening in the CPU. HWiNFO64 displays all four core voltages, which are labeled Core VID, and AIDA64 will display all four core voltages (the latest versions of course!)
Returning the board is a waste of time, it's the ASR UEFI/BIOS and A-Tuning that is wrong. I posted a thread about this in the ASR TTown forum, and ASRock acknowledged the issue and I am waiting on a UEFI update for my board.
Yes, Haswell is different than previous Intel CPUs, but that "Vcore" reading is a major, basic error by ASRock. They will no doubt pay for it, with all the returned boards. How in the world did this bug get past testing?