This 64GB memory is 100% compatible with QNAP TDS-16489U-SB2. The following technical specifications should be considered in advance: RDIMM and RDIMM 3DS (Registered DIMM) or LRDIMM and LRDIMM 3DS (Load Reduced DIMM) RAM memory can be installed in the unit. LRDIMM memories are recommended when large memory capacities are to be achieved. RDIMM and RDIMM 3DS memory modules cannot be operated mixed together with LRDIMM and LRDIMM 3DS RAM. If a memory expansion is to be carried out with the already existing RAM memories, it must be checked which basic memory technology (RDIMM / LRDIMM) is available. If memory modules are offered with higher clock rates than specified by the system, the memory clock is automatically adjusted to the system specifications. Memory for Intel Xeon CPUs: CPU / System RDIMM LRDIMM Xeon E5-16xx v3 Xeon E5-26xx v3 Xeon E5-46xx v3 8GB RDIMM 16GB RDIMM 32GB RDIMM 64GB RDIMM DDP 128GB RDIMM 3DS 256GB RDIMM 3DS 32GB LRDIMM 64GB LRDIMM DDP 128GB LRDIMM DDP 128GB LRDIMM 3DS 256GB LRDIMM 3DS.