Intel Xeon E5645 's Advantages
Lower TDP (80W vs 135W)
Intel Xeon E5 1691 v3 's Advantages
Released 4 years and 6 months late
Higher specification of memory (2133 vs 3)
Newer PCIe version (3 vs 2)
Higher base frequency (2.5GHz vs 2.4GHz)
Larger L3 cache size (35MB vs 12MB)
More modern manufacturing process (22nm vs 32nm)