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First, you cannot use XMP and the RAM MUST be set manually. Next, high frequency RAM in (1) kit should yield the Rated Frequency and CAS Timings. However, when mixing, yes this is a mix you might NOT get the Rated 'per set' Frequency and CAS. In addition, you are really pushing the IMC so the VCCIO Voltage might also need to be increased to 1.20v.
DDR3-2133 9-11-9-28-2N @ 1.60v
Next, in the BIOS manually set the Frequency, CAS Timings, DRAM Voltage -> 1.60~1.65v and the VCCIO -> 1.20v.
Failure, try a more standardized JEDEC -> DDR3-2133 10-10-10-30-2N @ 1.60v <or> 11-11-11-30-2N @ 1.60~1.65v and the VCCIO -> 1.20v.