I upgraded my RAM with 4 8GB Kingston HyperX 2133MHz (11-12-13) and I get memory errors with Rember. I'm also getting somewhat frequent application and OS X crashes that I neither get on my rMBP nor before the RAM upgrade. Rember gave me the following error: FAILURE! Data mismatch at local BUFA address 0x0000000496ca2ec8, BUFB address 0x000000082cd426c8 BUFA Data: 0x7edb584effe57bd9, BUFB Data: 0x7edb584effe57bf9 Since I couldn't match this memory address to a RAM bank, I tried to test the RAM modules 2 by 2 until I could isolate the culprit. But here's the weird thing: The memory issues only occur when I use all 4 modules. When I use any 2, the tests never failed. I tried them in bank 1 and 3 or 2 and 4, but they work fine regardless. So basically I can currently use my iMac with 16GB, no matter which modules or banks I am using, but I can't use all 4 at once. Is there any way to diagnose what could be the cause for that?