Tout simplement parce que certaines cartes-mères n'acceptent que des barrettes de 8 Go maximum par slot
4 x DDR4 DIMM sockets supporting up to 64 GB of system memory
* Due to a Windows 32-bit operating system limitation, when more than 4 GB of physical memory is installed, the actual memory size displayed will be less than the size of the physical memory installed.
Dual channel memory architecture
Support for DDR4 3800(O.C)/3733(O.C)/3666(O.C) /3600(O.C.) /3466(O.C.) /3400(O.C.) /3333(O.C.) /3300(O.C.) /3200(O.C.) /3000(O.C.) /2800(O.C.) /2666(O.C.) /2400(O.C.) /2133 MHz memory modules
Support for ECC UDIMM 1Rx8/2Rx8 memory modules (operate in non-ECC mode)
Support for non-ECC UDIMM 1Rx8/2Rx8/1Rx16 memory modules
Support for Extreme Memory Profile (XMP) memory modules
(Please refer "Memory Support List" for more information.)