Questions about ASUS Prime X299-A

The mainboard supports RAM up to 4133 MHz. For RAM from 2666 MHz, the XMP (Extreme Memory Profile) must be activated in the bios so that the full clock rate is reached. Otherwise, the RAM will only run at 2666 MHz.

The memory clock depends on the CPU, for an i9 it is DDR4 2666 MHZ. Since you have an open multiplier with these CPUs anyway, you don't necessarily have to overclock the rams as well, since they are usually overclocked. However, whether e.g. 4133 MHZ rams run at full speed on your board also depends on the memory controller in your CPU.

The Asus PRIME X299-DELUXE has additional Wi-Fi, Bluetooth, 4 x USB 2.0 instead of 2, 2 x LAN (RJ45) port(s) instead of 1. Furthermore, it has additional internal connections. The best thing to do is to go to the Asus homepage and add both motherboards to the comparison list, then you can see the differences: https://www.asus.com/ch-de/Motherboards/PRIME-X299-A/ https://www.asus.com/ch-de/Motherboards/PRIME-X299-DELUXE/