The E5-1620 v2 the OP is running does have an unlocked multiplier.
Here's a list of Xeon CPUs with unlocked multipliers according to overclocking results from HWBOT:
W5580 (most probably not unlocked, despite of one CPU-Z validation; please see also https://forums.servethehome.com/ind...h-an-open-multiplier.15983/page-5#post-209642)
W5590 (most probably not unlocked)
E5-1620 (source - max CPU multiplier is 43, just like the i7-3820)
E5-1620 v2 (source)
I've been running an overclocked E5-1620 Xeon for 6 years or so in an X79 rig:
That's the exact list I saw when i was thinking of which Xeon to get!!!
This is my Xeon
The mult values toggle from 37 to 39 but never once goes to 40 like cpu-z detects it should be able to go to.
I followed the Ivy bridge overclocking guide in EarthDog's sig but nothing works :-(