Intel Xeon X5650 's Advantages
Higher base frequency (2.666GHz vs 2.2GHz)
Larger L3 cache size (12MB vs 1.5MB)
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)