The latest Intel i-9000 series processors and closely related Xeon E-2100 CPUs can handle up to 128 GB of main memory. This requires a motherboard with four DIMM sockets, four 32-GB memory bay without buffer, and a current BIOS.
This latest provides Asus now for motherboards with the Z390 chipset, at least as beta versions. They contain a new Memory Reference Code (MRC), the Intel for the initialization of 32GB programmed UDIMMs with 16 Gigabit chips.
The problem: these 32 GB UDIMMs are not available yet. The only module on the Asus compatibility list is a DIMM type J4BGUS2G8QHBC of the little-known company SL Link, a provider of integrated system manufacturers (SL Link Memory Business Goup, SLL MBG). According to the list of qualified suppliers (QVL), the SL-Link module is equipped with Samsung chips of the DDR4-2666 speed class.
Samsung itself records the internal M378A4G43MB1-CTD module on the website, but it is not even available anywhere.
Registered DIMMs (RDIMM) and low-load DIMMs (LRDIMMs) have been available for more than 32 GB, but do not work on motherboards for desktop PC processors.
BIOS also for F processors
The new BIOS versions, for example in the 0802 version for the Asus Prime Z390-A and ROG Strix Z390-E games, also allow the use of the new "F" processors without GPU, such as the Core i9-9900KF. But these processors are not available yet.
MSI and Gigabyte also have BIOS updates for ready F types.