Solved. Corsair DDR4 2666MHz DRAM Frequency reported as 665.1 MHz in CPU-Z? | PCSPECIALIST
Why Task Manager shows 1333 Mhz and not 2666 Mhz despite adding 2*2GB 1333 Mhz (DDR3 KIT) and CPU-Z shows Dual Channel & DRAM Frequency at 665 Mhz? - Quora
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