Please visit the following link for CPU support table of A990FXM-A V1.0. ECS recommends users to use these CPUs with this motherboard for better compatibility and stability. This model has 4 x 240-pin DDR3 DIMM slots, each DIMM slot supports up to 8GB memory module, total is 32GB. It needs to update service BIOS to support 32GB memory.
CPU support table: