There are several webpages where you can check benchmarks, please check these PassMark - [Dual CPU] Intel Xeon E7- 4870 @ 2.40GHz - Price performance comparison , Intel Xeon E7-8893 v3 and let us know if these work for you.
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You´re right, I have been searching for benchmark reports for this processor but nothing has come out. From our end the official site to check specifications for products is Intel® Xeon® Processor E7-8893 v3 (45M Cache, 3.20 GHz) Specifications. Maybe you could try contacting PassMark Support Home Page in order to request a benchmark for this processor.