This 128GB memory is 100% compatible with ASRock Fatal1ty X99X Killer.
Memory for Core i7 5th Generation CPU: Optimal performance can be achieved with 4 or 8 identical memories per CPU. If an i7 processor is used, UDIMM memory modules must be installed. Memory for Xeon CPU: If a XEON CPU is used, ECC and RDIMM memory must be used. ECC DIMM (with error correction code) or RDIMM (Registered DIMM) RAM memory can be installed in the unit. RDIMM memories are recommended when large memory capacities are to be achieved. The different memory technologies (ECC / RDIMM) must not be mixed. If a memory expansion is to be carried out with the already existing RAM memories, it must be checked which memory technology (ECC / RDIMM) is available. CPU in the system UDIMM UDIMM ECC RDIMM Which memory technology can be used, depending on the CPU?Depending on the CPU Core i7-5960X Core i7-5930K Core i7-5820K 4GB UDIMM 8GB UDIMM 16GB UDIMM 32GB UDIMM Xeon E5-1600 v3 Xeon E5-2600 v3 8GB UDIMM ECC 8GB RDIMM 16GB RDIMM 32GB RDIMM 64GB RDIMM DDP 128GB RDIMM 3DS 256GB RDIMM 3DS.