O Linux está detectando apenas 2 GB de RAM [fechado]

Question

Eu recentemente instalei o antergos, a distro do Arch Linux. Eu tenho 6GB de RAM e apenas 2GB estão sendo detectados. Eu instalei a versão de 64 bits. Na BIOS, há 6 GB de memória. Eu também usei o Ubuntu e ele detecta 2GB também. Outras distribuições Linux fazem o mesmo. Eu também recoloquei meus slots de RAM sem sorte.

Eu tentei o seguinte:

$ free -m

              total        used        free      shared  buff/cache   available
Mem:           1964        1411          80          37         472         596
Swap:          3814           0        3814

lshw -c memory

  *-cache:0
       description: L1 cache
       physical id: 5
       slot: L1-Cache
       size: 384KiB
       capacity: 384KiB
       clock: 1GHz (1.0ns)
       capabilities: pipeline-burst internal write-back unified
       configuration: level=1
  *-cache:1
       description: L2 cache
       physical id: 6
       slot: L2-Cache
       size: 8MiB
       capacity: 8MiB
       clock: 1GHz (1.0ns)
       capabilities: pipeline-burst internal write-back unified
       configuration: level=2
  *-cache:2
       description: L3 cache
       physical id: 7
       slot: L3-Cache
       size: 8MiB
       capacity: 8MiB
       clock: 1GHz (1.0ns)
       capabilities: pipeline-burst internal write-back unified
       configuration: level=3
  *-memory
       description: System Memory
       physical id: 2c
       slot: System board or motherboard
       size: 6GiB
     *-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 Unbuffered (Unregistered) 667 MHz (1.5 ns)
          product: 1333EL Series
          vendor: Undefined
          physical id: 1
          serial: 00000000
          slot: Node0_Dimm1
          size: 2GiB
          width: 64 bits
          clock: 667MHz (1.5ns)
     *-bank:2
          description: DIMM DDR3 Synchronous Unbuffered (Unregistered) 667 MHz (1.5 ns)
          product: CMZ8GX3M2A160
          vendor: Corsair
          physical id: 2
          serial: 00000000
          slot: Node0_Dimm2
          size: 4GiB
          width: 64 bits
          clock: 667MHz (1.5ns)
     *-bank:3
          description: DIMM Synchronous [empty]
          product: Dimm3_PartNum
          vendor: Dimm3_Manufacturer
          physical id: 3
          serial: Dimm3_SerNum
          slot: Node0_Dimm3

# lshw -short | grep 'System Memory'

/0/2c                         memory      6GiB System Memory

$ uname -a

Linux <hostname> 4.12.4-1-ARCH #1 SMP PREEMPT Fri Jul 28 18:54:18 UTC 2017 x86_64 GNU/Linux

dmesg

[    0.000000] Linux version 4.12.4-1-ARCH (builduser@nspawn-9860) (gcc version 7.1.1 20170630 (GCC) ) #1 SMP PREEMPT Fri Jul 28 18:54:18 UTC 2017
[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-linux root=UUID=d597d2b0-dbcd-4e9b-8326-df9ce1547828 rw quiet resume=UUID=30a347fd-841f-4417-9dfe-c5b5ac793d4c
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
[    0.000000] e820: BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009ffff] usable
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007d478fff] usable
[    0.000000] BIOS-e820: [mem 0x000000007d479000-0x000000007da36fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000007da37000-0x000000007de34fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007de35000-0x000000007e101fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000007e102000-0x000000007e154fff] type 20
[    0.000000] BIOS-e820: [mem 0x000000007e155000-0x000000007e155fff] usable
[    0.000000] BIOS-e820: [mem 0x000000007e156000-0x000000007e35bfff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007e35c000-0x000000007e7fffff] usable
[    0.000000] BIOS-e820: [mem 0x00000000f8000000-0x00000000fbffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec10000-0x00000000fec10fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fec20000-0x00000000fec20fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed00000-0x00000000fed00fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed61000-0x00000000fed70fff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed80000-0x00000000fed8ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fef00000-0x00000000ffffffff] reserved
[    0.000000] NX (Execute Disable) protection: active