Asrock might call the system something different? It might have to be manually enabled, as technically it's running the CPU 'out of spec'. On my Asus motherboard (I'm also on Ivybridge), I think it's automatically enabled if you activate the XMP profile. I assume you've got the most up to date BIOS for your motherboard?
Edit!
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Here's an article about it (a couple of years old, mind):
http://www.anandtech.com/show/6214/m...about-free-mhz