我最近购买了一台配备 4x8 GB RAM 的新台式电脑。但是，操作系统（Ubuntu 16.04，64 位）仅报告 24 GB RAM，而不是 32。我已经对棒进行了物理检查，它们安装正确。
我知道操作系统可能会占用一些内存，但由于缺少 8 GB RAM 似乎过多，而且 3x8 等于 24，我想我应该询问比我更有经验的人。有些工具给我提供了相互矛盾的信息（如下所述）——我不确定发生了什么，也找不到任何可以解决我的问题的东西，所以我在这里发帖。
让我从相关硬件：
- 主板：Asrock 970M Pro3 970（最高支持64 GB）
- 内存：G.Skill D332GB 1600-999 RipjawsX K4 GSK，4x8 GB
- GPU：华硕 4GB D5 GTX 1050 TI PH（我在某处读到 GPU 占用了一些 RAM，不确定这在这里是否重要......）
我已经尝试过的：
这就是有趣的地方......
- BIOS 正确报告所有 4 个 RAM 棒
sudo dmidecode --type memory还检测所有 4 根棍子sudo lshw -class memory也显示 32GB RAM
然而...
- “关于这台计算机”报告 23.5 GiB
htop还报告23.5Gcat /proc/meminfo输出 24660520 kBfree -m看到 24082 MB RAM- 运行 memtest 仅测试了 24 GB RAM（未发现错误）
有人能解释一下发生了什么事吗？这是预期的行为还是有什么问题？
这是完整的命令的输出上文提到的：
sudo dmidecode --类型内存
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 2.7 present.
Handle 0x000D, 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 0x000F, DMI type 17, 34 bytes
Memory Device
Array Handle: 0x000D
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 8192 MB
Form Factor: DIMM
Set: None
Locator: A1_DIMM0
Bank Locator: A1_BANK0
Type: DDR3
Type Detail: Synchronous Unbuffered (Unregistered)
Speed: 1333 MHz
Manufacturer: Undefined
Serial Number: 00000000
Asset Tag: A1_AssetTagNum0
Part Number: F3-1600C9-8GXM
Rank: 2
Configured Clock Speed: 667 MHz
Handle 0x0011, DMI type 17, 34 bytes
Memory Device
Array Handle: 0x000D
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 8192 MB
Form Factor: DIMM
Set: None
Locator: A1_DIMM1
Bank Locator: A1_BANK1
Type: DDR3
Type Detail: Synchronous Unbuffered (Unregistered)
Speed: 1333 MHz
Manufacturer: Undefined
Serial Number: 00000000
Asset Tag: A1_AssetTagNum1
Part Number: F3-1600C9-8GXM
Rank: 2
Configured Clock Speed: 667 MHz
Handle 0x0013, DMI type 17, 34 bytes
Memory Device
Array Handle: 0x000D
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 8192 MB
Form Factor: DIMM
Set: None
Locator: A1_DIMM2
Bank Locator: A1_BANK2
Type: DDR3
Type Detail: Synchronous Unbuffered (Unregistered)
Speed: 1333 MHz
Manufacturer: Undefined
Serial Number: 00000000
Asset Tag: A1_AssetTagNum2
Part Number: F3-1600C9-8GXM
Rank: 2
Configured Clock Speed: 667 MHz
Handle 0x0015, DMI type 17, 34 bytes
Memory Device
Array Handle: 0x000D
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 8192 MB
Form Factor: DIMM
Set: None
Locator: A1_DIMM3
Bank Locator: A1_BANK3
Type: DDR3
Type Detail: Synchronous Unbuffered (Unregistered)
Speed: 1333 MHz
Manufacturer: Undefined
Serial Number: 00000000
Asset Tag: A1_AssetTagNum3
Part Number: F3-1600C9-8GXM
Rank: 2
Configured Clock Speed: 667 MHz
sudo lshw 级内存
*-firmware
description: BIOS
vendor: American Megatrends Inc.
physical id: 0
version: P1.60
date: 06/17/2016
size: 64KiB
capacity: 4032KiB
capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification uefi
*-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: d
slot: System board or motherboard
size: 32GiB
*-bank:0
description: DIMM DDR3 Synchronous 1333 MHz (0,8 ns)
product: F3-1600C9-8GXM
vendor: Undefined
physical id: 0
serial: 00000000
slot: A1_DIMM0
size: 8GiB
width: 64 bits
clock: 1333MHz (0.8ns)
*-bank:1
description: DIMM DDR3 Synchronous 1333 MHz (0,8 ns)
product: F3-1600C9-8GXM
vendor: Undefined
physical id: 1
serial: 00000000
slot: A1_DIMM1
size: 8GiB
width: 64 bits
clock: 1333MHz (0.8ns)
*-bank:2
description: DIMM DDR3 Synchronous 1333 MHz (0,8 ns)
product: F3-1600C9-8GXM
vendor: Undefined
physical id: 2
serial: 00000000
slot: A1_DIMM2
size: 8GiB
width: 64 bits
clock: 1333MHz (0.8ns)
*-bank:3
description: DIMM DDR3 Synchronous 1333 MHz (0,8 ns)
product: F3-1600C9-8GXM
vendor: Undefined
physical id: 3
serial: 00000000
slot: A1_DIMM3
size: 8GiB
width: 64 bits
clock: 1333MHz (0.8ns)
猫 /proc/meminfo
MemTotal: 24660520 kB
MemFree: 21122376 kB
MemAvailable: 21926440 kB
Buffers: 140544 kB
Cached: 963872 kB
SwapCached: 0 kB
Active: 2574684 kB
Inactive: 554432 kB
Active(anon): 2027416 kB
Inactive(anon): 71840 kB
Active(file): 547268 kB
Inactive(file): 482592 kB
Unevictable: 48 kB
Mlocked: 48 kB
SwapTotal: 25137148 kB
SwapFree: 25137148 kB
Dirty: 72 kB
Writeback: 0 kB
AnonPages: 2024884 kB
Mapped: 426756 kB
Shmem: 74552 kB
Slab: 170052 kB
SReclaimable: 120684 kB
SUnreclaim: 49368 kB
KernelStack: 11760 kB
PageTables: 48856 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 37467408 kB
Committed_AS: 8069992 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB
HardwareCorrupted: 0 kB
AnonHugePages: 397312 kB
CmaTotal: 0 kB
CmaFree: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 277632 kB
DirectMap2M: 7032832 kB
DirectMap1G: 19922944 kB
自由-m
total used free shared buff/cache available
Mem: 24082 2263 20553 68 1264 21364
Swap: 24547 0 24547