Asus is prepping at least five motherboards on the basis of Intel's range-topping Z790 chipset that will support DDR4 memory. Also, the motherboards will support Intel's flagship 13th Generation Core 'Raptor Lake' processors and will thus be able to keep their existing high-performance memory modules. 

Asus is planning to launch two TUF Gaming (TUF Gaming Z790-Plus D4 and TUF Gaming Z790-Plus WiFi D4) and three Prime-series (Prime Z790-P D4, Prime Z790M-Plus D4, and Prime Z790-P WiFi D4) motherboards powered by Intel's Z790 chipset that will support DDR4 memory, based on EAC filing. The release of one product is not always guaranteed but there are three out of five motherboards that are on the list of South Korea's RRA regulator (1, 2, 3), so Asus is prepping DDR4-supporting Intel Z790 platforms. 

Asustek's TUF Gaming motherboards cater to demanding gamers who are looking for performance, reliability, and also overclock ability, all these at reasonable prices. Though TUF Gaming mainboards are listed below the company's ROG platforms in the company's hierarchy, these are the advanced motherboards having premium features. 

The Asus Prime family is placed below TUF Gaming but still offers premium features, enhanced voltage regulating modules (VRMs) to enable overclocking, and other tuning capabilities. Thus, it can be said to be a natural fit for the Prime Z790 family to include advanced LGA1700 motherboards that support DDR4 memory sticks. 

Whether you like it or not, DDR4 memory's days are limited and thus, Intel prefers to talk about DDR5 SDRAM, though its current 600-series and upcoming 700-series platforms support DDR4 and DDR5. But motherboard makers always try to offer what their customers want and many like to use good-old DDR4 for a while, and because of this both Asus and MSI will provide Z790-based platforms with DDR4. 

DDR4 memory is there for around seven years, and producers of high-end memory modules have sold a boatload of enthusiast-grade DDR4 modules with data transfer rates in DDR5's territory. Discarding those modules, won't make sense and so, keeping them for a few years would be reasonable. 

The biggest question about midrange Z790 motherboards for Intel's Raptor Lake processors is whether they will properly support the rumored 350W mode enabling ultimate turbo frequencies and thus, requiring an advanced voltage regulating module to deliver immaculate power to the CPU. TUF Gaming and Prime are premium motherboards but not as good as the Asus ROG family. It will be really amazing to see how different Intel Z790 platforms perform.