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I have AMD FX-8350 processors amd Gigabyte 970 Gaming G1 motherboard. both support 8+8 GB RAM. But when I installed Ubuntu 16.06 LTS only 8 GB RAM detected. Although im BIOS 16GB RAM is showing. Can anyone please help to find out the issue.

Output of sudo lshw -class memory (firmware and CPU cache entries removed):

  *-memory
       description: System Memory
       physical id: 2c
       slot: System board or motherboard
       size: 16GiB
     *-bank:0
          description: DIMM Synchronous [empty]
          product: Dimm0_PartNum
          vendor: Dimm0_Manufacturer
          physical id: 0
          serial: Dimm0_SerNum
          slot: Node0_Dimm0
     *-bank:1
          description: DIMM DDR3 Synchronous 800 MHz (1.2 ns)
          product: CT102464BD160
          vendor: Undefined
          physical id: 1
          serial: xxxxxx
          slot: Node0_Dimm1
          size: 8GiB
          width: 64 bits
          clock: 800MHz (1.2ns)
     *-bank:2
          description: DIMM DDR3 Synchronous 800 MHz (1.2 ns)
          product: CT102464BD160
          vendor: Undefined
          physical id: 2
          serial: xxxxxxx
          slot: Node0_Dimm2
          size: 8GiB
          width: 64 bits
          clock: 800MHz (1.2ns)
     *-bank:3
          description: DIMM Synchronous [empty]
          product: Dimm3_PartNum
          vendor: Dimm3_Manufacturer
          physical id: 3
          serial: Dimm3_SerNum
          slot: Node0_Dimm3

Output of free:

              total        used        free      shared  buff/cache   available
Mem:        8200928     1225344     4568440       26436     2407144     6636296
Swap:       8350716           0     8350716

Output of sudo dmidecode -t memory:

# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 2.7 present.

Handle 0x0008, DMI type 5, 24 bytes
Memory Controller Information
    Error Detecting Method: 64-bit ECC
    Error Correcting Capabilities:
        None
    Supported Interleave: One-way Interleave
    Current Interleave: One-way Interleave
    Maximum Memory Module Size: 2048 MB
    Maximum Total Memory Size: 8192 MB
    Supported Speeds:
        70 ns
        60 ns
    Supported Memory Types:
        DIMM
        SDRAM
    Memory Module Voltage: 3.3 V
    Associated Memory Slots: 4
        0x0009
        0x000A
        0x000B
        0x000C
    Enabled Error Correcting Capabilities:
        None

Handle 0x0009, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM0
    Bank Connections: 0 1
    Current Speed: 60 ns
    Type: DIMM SDRAM
    Installed Size: 536870912 MB (Single-bank Connection)
    Enabled Size: 536870912 MB (Single-bank Connection)
    Error Status: OK

Handle 0x000A, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM1
    Bank Connections: 2 3
    Current Speed: 60 ns
    Type: DIMM SDRAM
    Installed Size: 536870912 MB (Single-bank Connection)
    Enabled Size: 536870912 MB (Single-bank Connection)
    Error Status: OK

Handle 0x000B, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM2
    Bank Connections: 4 5
    Current Speed: 60 ns
    Type: DIMM SDRAM
    Installed Size: 536870912 MB (Single-bank Connection)
    Enabled Size: 536870912 MB (Single-bank Connection)
    Error Status: OK

Handle 0x000C, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM3
    Bank Connections: 6 7
    Current Speed: 60 ns
    Type: DIMM SDRAM
    Installed Size: 536870912 MB (Single-bank Connection)
    Enabled Size: 536870912 MB (Single-bank Connection)
    Error Status: OK

Handle 0x002C, DMI type 16, 23 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: None
    Maximum Capacity: 32 GB
    Error Information Handle: Not Provided
    Number Of Devices: 4

Handle 0x002E, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x002C
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: 64 bits
    Size: No Module Installed
    Form Factor: DIMM
    Set: None
    Locator: Node0_Dimm0
    Bank Locator: Node0_Bank0
    Type: Unknown
    Type Detail: Synchronous
    Speed: Unknown
    Manufacturer: Dimm0_Manufacturer
    Serial Number: Dimm0_SerNum
    Asset Tag: Dimm0_AssetTag
    Part Number: Dimm0_PartNum
    Rank: Unknown
    Configured Clock Speed: Unknown

Handle 0x0030, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x002C
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 8192 MB
    Form Factor: DIMM
    Set: None
    Locator: Node0_Dimm1
    Bank Locator: Node0_Bank0
    Type: DDR3
    Type Detail: Synchronous Unbuffered (Unregistered)
    Speed: 800 MHz
    Manufacturer: Undefined         
    Serial Number: E059EC0B    
    Asset Tag: Dimm1_AssetTag
    Part Number: CT102464BD160
    Rank: 2
    Configured Clock Speed: 800 MHz

Handle 0x0032, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x002C
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 8192 MB
    Form Factor: DIMM
    Set: None
    Locator: Node0_Dimm2
    Bank Locator: Node0_Bank0
    Type: DDR3
    Type Detail: Synchronous Unbuffered (Unregistered)
    Speed: 800 MHz
    Manufacturer: Undefined         
    Serial Number: E059EC5D    
    Asset Tag: Dimm2_AssetTag
    Part Number: CT102464BD160
    Rank: 2
    Configured Clock Speed: 800 MHz

Handle 0x0034, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x002C
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: 64 bits
    Size: No Module Installed
    Form Factor: DIMM
    Set: None
    Locator: Node0_Dimm3
    Bank Locator: Node0_Bank0
    Type: Unknown
    Type Detail: Synchronous
    Speed: Unknown
    Manufacturer: Dimm3_Manufacturer
    Serial Number: Dimm3_SerNum
    Asset Tag: Dimm3_AssetTag
    Part Number: Dimm3_PartNum
    Rank: Unknown
    Configured Clock Speed: Unknown

Output of free after swapping the memory slots:

              total        used        free      shared  buff/cache   available
Mem:       16458456      807424    14920452       23940      730580    15312852
Swap:       8350716           0     8350716
  • Please edit and post the results of sudo lshw -class memory – user692175 Aug 19 '17 at 12:23
  • Please also post the output of free command. – Pilot6 Aug 19 '17 at 12:30
  • @Pilot6 What do you think of it? It shows both DIMMs and yet free indicates only half is used? – user692175 Aug 19 '17 at 12:37
  • Can you boot into memtest and check how much that recognizes? Could you try and place the memory banks in different slots? It looks weird to me that they are in slots 1 and 2 and not e.g. in 0 and 2 or 1 and 3, although your output doesn't look like you have dual channel RAM anyway. You could also add the output of sudo dmidecode -t memory to the question. – Byte Commander Aug 19 '17 at 12:58
  • Thanks @Byte Commander: I have changed the slot as 1&3 and it worked. Now I can see free as 16GB. – Sohail Hassan Aug 19 '17 at 13:25
4

You have 4 memory slots numbered 0, 1, 2 and 3.

Normally (at least on dual-channel RAM mainboards), if you have only 2 of 4 slots used, the RAM bricks are inserted either into the even or the odd slots. Often the sockets also have two different colours to indicate this.

As the output of sudo lshw -c memory suggests, your bricks are placed in the slots 1 and 2 though.

I would suggest switching their positions so that both bricks are either in even (0, 2) or odd (1, 3) slots. Consult your mainboard manual for the exact recommended order.

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