Several manufacturers have released bios updates for the AMD-AM5 motherboards, giving the boards support for 24GB and 48GB DDR5 memory dimms. Previously, PCs with these modules would not boot. This support was already there on Intel DDR5 motherboards.
With the support of 48GB memory modules, the AM5 motherboards can be equipped with up to 192GB of memory. Previously this was 128GB. Some Intel 700 and 600 motherboards already had this support, but not yet on AM5 motherboards. AM5 PCs with 24GB or 48GB bars will not boot without this support, it was previously found.
Presumably the 24GB and 48GB support is in Agesa version 22.214.171.124. Agesa is AMD’s software on which manufacturers base their bios. ASUS, ASRock, gigabytes and MSI claim to have released an Agesa 126.96.36.199 update to motherboards. In many cases, the bios updates also contain the new measures to limit the soc voltage of Ryzen 7000 CPUs.
48GB modules on an AM5 motherboard from MSI