Intel Xeon D 1520 's Advantages
Released 3 years late
Higher specification of memory (4 vs 3)
More modern manufacturing process (14nm vs 32nm)
Lower TDP (45W vs 130W)
Intel Xeon E5 1660 's Advantages
Higher base frequency (3.3GHz vs 2.2GHz)
Larger L3 cache size (15MB vs 1.5MB)