16.04LTS 64bit видит только 3,9 ГБ памяти из 8 ГБ

free -m output :

  total used free shared buff/cache available Mem: 3951 1291 1720 41 939 2362 Swap: 4094 0 4094 

Выход dmidecode :

 Handle 0x000C, DMI type 16, 15 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: 2 Handle 0x000D, DMI type 19, 15 bytes Memory Array Mapped Address Starting Address: 0x00000000000 Ending Address: 0x0012FFFFFFF Range Size: 4864 MB Physical Array Handle: 0x000C Partition Width: 1 Handle 0x000E, DMI type 17, 28 bytes Memory Device Array Handle: 0x000C 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: Other Type Detail: Synchronous Speed: 533 MHz Manufacturer: Corsair Serial Number: 00000000 Asset Tag: AssetTagNum0 Part Number: CMV4GX3M1A1333C9 Rank: Unknown Handle 0x000F, DMI type 20, 19 bytes Memory Device Mapped Address Starting Address: 0x00000000000 Ending Address: 0x000FFFFFFFF Range Size: 4 GB Physical Device Handle: 0x000E Memory Array Mapped Address Handle: 0x000D Partition Row Position: 1 Handle 0x0010, DMI type 17, 28 bytes Memory Device Array Handle: 0x000C Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 4096 MB Form Factor: DIMM Set: None Locator: DIMM1 Bank Locator: BANK1 Type: Other Type Detail: Synchronous Speed: 533 MHz Manufacturer: Corsair Serial Number: 00000000 Asset Tag: AssetTagNum1 Part Number: CMV4GX3M1A1333C9 Rank: Unknown Handle 0x0011, DMI type 20, 19 bytes Memory Device Mapped Address Starting Address: 0x00100000000 Ending Address: 0x001FFFFFFFF Range Size: 4 GB Physical Device Handle: 0x0010 Memory Array Mapped Address Handle: 0x000D Partition Row Position: 1