To get maximum capacity of RAM supported by server use following command.
$ dmidecode -t 16
# dmidecode 2.11
SMBIOS 2.7 present.
Handle 0x0008, DMI type 16, 23 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 16 GB
Error Information Handle: Not Provided
Number Of Devices: 2
Above output shows maximum capacity supported by server is 16GB and number of RAM devices supported by server is 2.