AMD Radeon R9 390 X2 's Advantages
Released 2 years and 5 months late
More VRAM (8GB vs 3GB)
Larger VRAM bandwidth (345.6GB/s vs 288.0GB/s)
512 additional rendering cores
AMD Radeon HD 8990 OEM 's Advantages
Boost Clock1000MHz
Lower TDP (375W vs 580W)