% sudo dmidecode -d /dev/mem
...
Handle 0x0033, DMI type 17, 28 bytes
Memory Device
        Array Handle: 0x0032
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 4096 MB
        Form Factor: SODIMM
        Set: None
        Locator: ChannelA-DIMM0
        Bank Locator: BANK 0
        Type: DDR3
        Type Detail: Synchronous
        Speed: 1333 MHz
        Manufacturer: Samsung
        Serial Number: ...
        Asset Tag: ...
        Part Number: M471B5273DH0-CH9
        Rank: Unknown
Handle 0x0035, DMI type 17, 28 bytes
Memory Device
        Array Handle: 0x0032
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 2048 MB
        Form Factor: SODIMM
        Set: None
        Locator: ChannelB-DIMM0
        Bank Locator: BANK 2
        Type: DDR3
        Type Detail: Synchronous
        Speed: 1333 MHz
        Manufacturer: Samsung
        Serial Number: ...
        Asset Tag: ...
        Part Number: M471B5773DH0-CH9
        Rank: Unknown