Intel Xeon D 1520 's Advantages
Released 5 years late
Higher specification of memory (4 vs 3)
Newer PCIe version (3 vs 2)
More modern manufacturing process (14nm vs 32nm)
Lower TDP (45W vs 95W)
Intel Xeon X5660 's Advantages
Higher base frequency (2.8GHz vs 2.2GHz)
Larger L3 cache size (12MB vs 1.5MB)