Xeon E6540 's Advantages
Higher specification of memory (1333 vs 3)
Intel Xeon E5 2658 's Advantages
Released 2 years late
Newer PCIe version (3 vs 2)
Higher base frequency (2.1GHz vs 2GHz)
Larger L3 cache size (20MB vs 18MB)
More modern manufacturing process (32nm vs 45nm)
Lower TDP (95W vs 105W)