ASUS PRIME X399-A
Motherboard, from 2017 25 hardware reports
Memory
Up to 128 GB
8 full-size slots
SSD slots
Coming next
Checked from separate sources
Upgradable
Yes. 8 slots, up to 128 GB seen working.
It takes DDR4-2133 full-size sticks (DIMM).
- Slots
- 8 DIMM slots
- Type
- DDR4-2133 288-pin DIMM
- Most seen working
- 128 GB in two or more machines
- Firmware says
- 512 GB maximum (often wrong, so we show what machines run)
- How sure
- 25 of 25 reports show this layout
See 16 GB DDR4-2133 DIMM on AmazonOpens an Amazon search for this exact spec.
Worked out from 25 hardware reports of this motherboard. Sources and method. Updated 9 Nov 2026.
8 full-size slots
Illustration Questions
Can I upgrade the RAM in the ASUS PRIME X399-A?
Yes. 8 slots, up to 128 GB seen working. It takes DDR4-2133 full-size sticks (DIMM).
What type of RAM does the ASUS PRIME X399-A use?
DDR4-2133 full-size sticks (DIMM, 288-pin).
How much RAM can the ASUS PRIME X399-A take?
Machines in the reports run up to 128 GB. The firmware reports a maximum of 512 GB, a figure that is often wrong.
Is this my motherboard?
The model name is printed on the board, usually between the memory slots or near the CPU socket. In Windows, open System Information and look at "BaseBoard Product"; it should read PRIME X399-A.