You can get this information by visiting your BIOS setup menu. Another option is to use dmidecode command to dump bios memory information from a shell prompt:
# dmidecode --type 16
# dmidecode 2.11 SMBIOS 2.5 present. Handle 0x0016, DMI type 16, 15 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: Single-bit ECC Maximum Capacity: 64 GB Error Information Handle: Not Provided Number Of Devices: 8
To see memory speed and other information, enter:
# dmidecode --type memory
