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I've installed 8GB of RAM (2x4GB) in my computer. Before I have only 4GB (1x4GB), and I've installed the new cards one where the oldest was and the other in the other slot of the same type. But if I check my Ubuntu's details or htop, it only shows 4GB (3'8GB). My motherboard is Asus P7H55-M. In windows it detects 8GB but it says that it only can use 4GB, don't know why. This are my outputs. (there are in spanish)

free -h:

             total       usado       libre     compart.    búffers 
    almac.
Mem:          3,8G       2,2G       1,6G        18M       119M       869M
-/+ buffers/cache:       1,2G       2,6G
Intercambio:       4,5G         0B       4,5G

sudo dmidecode --type memory:

SMBIOS 2.6 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:
        Other
    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: Unknown
    Type: DIMM SDRAM
    Installed Size: 4096 MB (Double-bank Connection)
    Enabled Size: 4096 MB (Double-bank Connection)
    Error Status: OK

Handle 0x000A, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM1
    Bank Connections: 2 3
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: Not Installed
    Enabled Size: Not Installed
    Error Status: OK

Handle 0x000B, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM2
    Bank Connections: 4 5
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: 4096 MB (Double-bank Connection)
    Enabled Size: 4096 MB (Double-bank Connection)
    Error Status: OK

Handle 0x000C, DMI type 6, 12 bytes
Memory Module Information
    Socket Designation: DIMM3
    Bank Connections: 6 7
    Current Speed: Unknown
    Type: DIMM SDRAM
    Installed Size: Not Installed
    Enabled Size: Not Installed
    Error Status: OK

Handle 0x0036, DMI type 16, 15 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: 4

Handle 0x0038, DMI type 17, 28 bytes
Memory Device
    Array Handle: 0x0036
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 4096 MB
    Form Factor: DIMM
    Set: None
    Locator: DIMM0
    Bank Locator: BANK0
    Type: DDR
    Type Detail: Synchronous
    Speed: 1333 MHz
    Manufacturer: Manufacturer0
    Serial Number: SerNum0
    Asset Tag: AssetTagNum0
    Part Number: PartNum0
    Rank: Unknown

Handle 0x003A, DMI type 17, 28 bytes
Memory Device
    Array Handle: 0x0036
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: Unknown
    Size: No Module Installed
    Form Factor: DIMM
    Set: None
    Locator: DIMM1
    Bank Locator: BANK1
    Type: Unknown
    Type Detail: Unknown
    Speed: Unknown
    Manufacturer: Manufacturer1
    Serial Number: SerNum1
    Asset Tag: AssetTagNum1
    Part Number: PartNum1
    Rank: Unknown

Handle 0x003C, DMI type 17, 28 bytes
Memory Device
    Array Handle: 0x0036
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: 4096 MB
    Form Factor: DIMM
    Set: None
    Locator: DIMM2
    Bank Locator: BANK2
    Type: DDR
    Type Detail: Synchronous
    Speed: 1333 MHz
    Manufacturer: Manufacturer2
    Serial Number: SerNum2
    Asset Tag: AssetTagNum2
    Part Number: PartNum2
    Rank: Unknown

Handle 0x003E, DMI type 17, 28 bytes
Memory Device
    Array Handle: 0x0036
    Error Information Handle: Not Provided
    Total Width: Unknown
    Data Width: Unknown
    Size: No Module Installed
    Form Factor: DIMM
    Set: None
    Locator: DIMM3
    Bank Locator: BANK3
    Type: Unknown
    Type Detail: Unknown
    Speed: Unknown
    Manufacturer: Manufacturer3
    Serial Number: SerNum3
    Asset Tag: AssetTagNum3
    Part Number: PartNum3
    Rank: Unknown

With dmicoded it shows that there are two RAMs of 4GB.

And, obviously I'm using a 64bits kernel:

Linux m0skva 3.13.0-53-generic #89-Ubuntu SMP Wed May 20 10:34:39 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

The BIOS memory remaping is enabled. I don't know what more to do.

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  • What's the model of your computer? May 27, 2015 at 10:57
  • It's a desktop. Processor i5 760 @ 2.8GHz x 4
    – aSoler
    May 27, 2015 at 10:59
  • Place them on the motherboard next to each other ? i.e in BANK0 and BANK1
    – solsTiCe
    May 27, 2015 at 11:07
  • The motherboard have 4 slots, i.e BANK0A, BANK1A, BANK0B, BANK1B, and there are in 1A and 1B. There are two colors and there're in the same color.
    – aSoler
    May 27, 2015 at 11:10

3 Answers 3

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Memory Controller Information
Maximum Memory Module Size: 2048 MB

This part of the output from above would explain what you are seeing. Can you confirm the motherboard used, or check the maximum capacity it will accept for each individual DIMM?

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  • Yeah, I read that and it as strange, because before I have a 4GB RAM memory and it worked perfect.
    – aSoler
    May 27, 2015 at 11:20
  • Max memory module size refers to the maximum size of each RAM card or module. Before, you had 4 1GB sticks, which are all smaller than 2GB. Now you have 2 4GB, so 2GB of each is getting cut off. You need 4 2GB sticks. @alvarSoler May 27, 2015 at 11:51
  • @Zacharee1 no, before I had 1x4GB.
    – aSoler
    May 27, 2015 at 12:22
  • Did your computer tell you you had 4GB when you had it in? May 27, 2015 at 14:17
  • Yes (3'8Gb more or less), I've used it for years. That's why I'm so confused. @Zacharee1
    – aSoler
    May 27, 2015 at 15:04
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Sharing my experience: I struggled with this issue all day. In my case, I realized the blue and white slots in my gigabyte motherboard were the issue. Once I put my 4gb ram sticks in the same colored slot(blue) it all worked out :)

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Try to match your slots so that the pairs reflects the same speed and manufacturer of the sticks.

Check your CPU speed. Go in the bios and slow it down to accommodate the slowest memory. You might have to test by going slower than the specification to get to a point where the full memory is working.

After you have a working configuration, of course if it works as a results of slowing down the process speed, invest into changing the slowest sticks will faster sticks.

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