you honestly have no clue what you're talking about
that pretty much confirms that it's a glitch and those aren't your actual clocks. I'd say bring it back down to your max OC before artifacting and be happy at that because you'll get a higher score in 3dmark and better performance than stock or ur current OC
oh another note, do your 3dmark test at 1280x1024, its the standard resolution for that test and is what everyone here compares scores by, you might see more of a difference at that resolution
anyways, just from experience, i find that if you overclock the ram on your gpu that you get higher stable fps than oc'in the core...