MSI Z390A-PRO supports up to four RAM modules.
MSI Z390A-PRO supports up to four RAM modules.
Using 2x sticks versus 4x sticks puts extra load on the Integrated Memory Controller. Adjustments might be required such as lowering the clock speed, increasing voltage, or optimizing timing settings. As discussed earlier, your friend could attempt DDR4-2666 XMP mode or manually set the DRAM frequency multiplier to values like DDR4-2933 or 2800. They might also increase the DRAM voltage from 1.35V to 1.40V, and slightly raise VCCSA or VCCIO if necessary. Adding more DIMMs or dual-rank modules could necessitate higher VCSSA and VCCIO than the default settings suggest.