Vid on Haswell-E imho is useless, same 4.5 GHz @ voltage on air. all depends from CB and cpu itself regarding scaling
My golden USA cpu has vid 0.992v, does 4.5 ghz @ 1.275v and 5.8 GHz 4-Way Gen 3,0 on ln2... just scales like crazy with cold
My best retail is also vid 0.992v, does 4.5 ghz @ 1.25v, 5.6 ghz @ 1.6v on ln2 cinebench