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I have a Lenovo motherboard with 2 4GB DIMMs. I see the 8GB when selecting and running the a memory test from the Ubuntu Grub bootup menu.

However when I boot up ubuntu 16.04, free only shows 4GB.

When I run dmidecode. I see the two 4GB DIMMs:

BIOS Information
    Vendor: LENOVO
    Version: I7KT32AUS
    Release Date: 12/26/2013
    Address: 0xF0000
    Runtime Size: 64 kB
    ROM Size: 4096 kB
...
Handle 0x0017, DMI type 16, 23 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: None
    Maximum Capacity: 8 GB
    Error Information Handle: Not Provided
    Number Of Devices: 4

Handle 0x0018, DMI type 19, 31 bytes
Memory Array Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x000FFFFFFFF
    Range Size: 4 GB
    Physical Array Handle: 0x0017
    Partition Width: 255

Handle 0x0019, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x0017
    Error Information Handle: Not Provided
    Total Width: 64 bits
    Data Width: 64 bits
    Size: No Module Installed
    Form Factor: SODIMM
    Set: None
    Locator: DIMM 0
    Bank Locator: CHANNEL B
    Type: DDR3
    Type Detail: None
    Speed: Unknown
    Manufacturer: A1_Manufacturer2
    Serial Number: A1_SerialNum2
    Asset Tag: A1_AssetTagNum2
    Part Number: A1_PartNum2
    Rank: Unknown
    Configured Clock Speed: Unknown

Handle 0x001A, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x0017
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: DIMM
Set: None
Locator: DIMM 1
Bank Locator: CHANNEL B
Type: DDR3
Type Detail: Synchronous Unbuffered (Unregistered)
Speed: 1600 MHz
Manufacturer: Samsung
Serial Number: 93FB5498
Asset Tag: A1_AssetTagNum3
Part Number: M378B5173QH0-CK0
Rank: 1
Configured Clock Speed: 1600 MHz

What seems odd and may explain the discrepancy is that I have one 4 GB Memory Array Mapped Address and one 4 GB Device Mapped Address.

Handle 0x0018, DMI type 19, 31 bytes
    Memory Array Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x000FFFFFFFF
    Range Size: 4 GB
    Physical Array Handle: 0x0017
    Partition Width: 255

....

Memory Device Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x000FFFFFFFF
    Range Size: 4 GB
    Physical Device Handle: 0x001A
    Memory Array Mapped Address Handle: 0x0018
    Partition Row Position: Unknown
    Interleave Position: Unknown
    Interleaved Data Depth: Unknown

I have not been able to find out what a Memory Device is and what a Memory Array is and what can set that.

More generally any thoughts on why only around 4GB is available and seen by free?

rocky
  • 807

0 Answers0