16GB RAM recognized in BIOS but only 8 in Windows

Hi wcondie,

The Inspiron All In One Inspiron 24 - 3455 system has 2 DIMM slots. The system accepts a memory capacity ranging from 2GB, 4GB, and 8GB. The memory type accepted is DDR3L 1600 MHz DIMM only. The computer supports a maximum of 8GB of memory when installed with two 4GB DIMMs.

Thanks for the input. Crucial insists it will take 8G per slot and that is what is currently installed.

Theoretically the machine shouldn't be running

You cant use high density ram if you could then the maximum ram would be 32 gigs and it would have 4 ram slots.  This won't change with crucial insisting that it works nor berating a dell support person.

If you install high-density memory on a motherboard that is not compatible with the module, it will not work or only recognize a portion of the memory.

Ranks are sub-units of a memory module which share the same address and data buses and are selected via CS (Chip Select)  in low level addressing. For example, take a memory module with 8 chips on each side, with each chip having 8 bit wide data bus,  then that module would have one rank for each side for a total of 2 ranks, if we define a rank to be 64 bits wide.  That's why High density is not sufficent for some chipsets because the BUS is 128 bits wide. This is also why only 1/2 of each dimm is working when 4 are used. You need RANK 4 ram due to the width of the bus.