Forgot about Dell gimping Turbo Boost on that firmware.
Another route is the PowerEdge T440 (tower server), which does respect Broadwell-EP turbo logic without a reflash. Not quite as quiet as a workstation, though.
It's not an issue with Dell it's an issue with how the chips themselves are designed. There are buggy microcodes in the Haswell-EP series which can be exploited to unlock FULL Turbo Boost on ALL cores of the CPUs. This is NOT possible on Broawdwell-EP.
Another route is the PowerEdge T440 (tower server), which does respect Broadwell-EP turbo logic without a reflash. Not quite as quiet as a workstation, though.