DDR4 SDRAM

DDR4 is the newest iteration in DRAM, loaded with new features that improve reliability, speed, power, and stacking capabilities for the enterprise, micro-server, ultrathin, tablet markets, automotive and embedded markets—industrial, consumer and connected home applications. With data rates reaching 2400 Mb/s, DDR4 increases performance up to 50% over DDR3. DDR4 also delivers a 20% reduction in voltage over DDR3—however, when DDR4’s additional power-saving features are taken into account, total overall power savings versus DDR3 can be as much as 35%.

DDR4 By Density

Reduce power up to 35% thanks to our low 1.2V option and other power-saving features.
 
Improve performance up to 50% compared to DDR3.
More pictures showing difference between DDR4 and DDR3.

DDR4 and DDR3 memory slot are different, so mini pc designed for DDR4 may not support DDR3, those mini pc designed for DDR3 also not support DDR4.

Here is two fanless mini pc models support DDR4: model FMP03B-i5-6360U with 2 DDR4 memory slot max 32G RAM; model FMP06-i3-6100U with 1 DDR4 memory slot max 16G RAM