Intels Apollo Lake CPUs can take up to 16GB DDR3L RAM at 1866MT/s speed in Non-ECC operation.
Optionally ECC can be used with reduced maximum operation speed of 1600MT/s.
These 16GB need to be split into two ranks of 8GB each. This means that each rank must be made of 8 Gigabit DDR3L components in a x8 organization.
The manufacturer Micron had the 8Gb MT41K1G8SN devices before, but these are now EOL. Industrial Temp or DDR3L-1866 versions were rarely or not available anyway.
A good option is to use the 8Gb DDR3L Intelligent Memory DRAM-components with part# IM8G08D3FCBG (Click the part# for direct link to the datasheet!)
These parts are available with up to DDR3L-1866 speed and also industrial temperature.
We have already tested them successfully on multiple boards with Apollo Lake CPUs as well as others like Broadwell, Baytrail, etc!
For customers having a SO-DIMM slot on their Apollo Lake boards, Intelligent Memory also offers 16GB modules with and without ECC.
16GB Non-ECC SO-DIMM Module Part# IMM2G64D3LSOD8AG (Click the part# for direct link to the datasheet!)
16GB Non-ECC SO-DIMM Module Part# IMM2G72D3LSOD8AG (Click the part# for direct link to the datasheet!)
A list of distributors can be found here: Where to buy | Intelligent Memory