OWC 24.0GB (3 x 8GB) PC3-10600 DDR3 ECC-R 1333MHz... at MacSales.com
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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