Rumor mill: AMD doesn't currently offer any CPU that supports LPDDR4X memory. However, if speculation from recent Linux patches is to be believed, that could change with AMD's next-gen APUs. The next-gen APUs will transition to a 7nm process node and feature Zen 2 cores. There's also speculation that Renoir will roll out with Vega 10 graphics, rather than Navi, but we'll have to wait and see.
A pair of Linux patches come with hints that AMD's next round of APUs, code-named Renoir, will boast LPDDR4X memory support. The first patch lists LPDDR4X as a supported memory type, while the second patch specifies the 4,266 MHz frequency.
The patches seemingly suggest that Renoir could arrive with a refined memory controller, which would be a welcome upgrade over the DDR4-2400 specification that Raven Ridge and Picasso support.
It seems German tech outlet ComputerBase and known hardware leaker Komachi_Ensaka were among the first to spot the lines of code referencing the memory upgrade.
[amd-gfx] [PATCH 10/23] drm/amd/display: Add Renoir resource (v2) https://t.co/53hkJMGhv9— 比屋定さんの戯れ言@Komachi (@KOMACHI_ENSAKA) August 29, 2019
Considering that AMD's Renoir APUs will battle Intel's Ice Lake mobile chips, which support both DDR4-3200 and LPDDR4-3733 and come with Intel's beefier Gen11 integrated graphics, AMD likely realized it needed to close the gap in memory support -- especially considering how much APUs benefit from faster memory.
Renoir is slated to be the successor to Picasso, and arrive some time in 2020.