I recently purchased a new Desktop PC with 4x8 GB RAM. However, the operating system (Ubuntu 16.04, 64 bit) only reports 24 GB RAM instead of 32. I already checked the sticks physically, they are installed correctly. I am aware that the OS might occupy some of the memory, but as 8 GB of missing RAM seems excessive and 3x8 equals 24 I figured I should ask people that have more experience than me. Some of the tools give me conflicting information (as described below) -- I am not sure what is going on and I couldn't find anything that solves my problem, so I'm posting here.Let me start with the relevant hardware:Mainboard: Asrock 970M Pro3 970 (supports up to 64 GB)RAM: G.Skill D332GB 1600-999 RipjawsX K4 GSK, 4x8 GBGPU: Asus 4GB D5 GTX 1050 TI PH (I read somewhere that the GPU occupies some of the RAM, not sure if that is important here...)What I have tried already:This is where it gets interesting...The BIOS reports all 4 RAM sticks correctlysudo dmidecode --type memory also detects all 4 stickssudo lshw -class memory shows 32GB RAM tooHowever...About this computer reports 23.5 GiBhtop also reports 23.5Gcat /proc/meminfo outputs 24660520 kBfree -m sees 24082 MB RAMrunning memtest only tested 24 GB of RAM (and found no errors)Can anybody explain what is going on? Is this expected behaviour or is there something wrong?Here is the full output of the commands mentioned above:sudo dmidecode --type memory# dmidecode 3.0Getting SMBIOS data from sysfs.SMBIOS 2.7 present.Handle 0x000D, DMI type 16, 23 bytesPhysical 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: 4Handle 0x000F, DMI type 17, 34 bytesMemory 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 MHzHandle 0x0011, DMI type 17, 34 bytesMemory 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 MHzHandle 0x0013, DMI type 17, 34 bytesMemory 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 MHzHandle 0x0015, DMI type 17, 34 bytesMemory 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 MHzsudo lshw -class memory  *-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)cat /proc/meminfoMemTotal:       24660520 kBMemFree:        21122376 kBMemAvailable:   21926440 kBBuffers:          140544 kBCached:           963872 kBSwapCached:            0 kBActive:          2574684 kBInactive:         554432 kBActive(anon):    2027416 kBInactive(anon):    71840 kBActive(file):     547268 kBInactive(file):   482592 kBUnevictable:          48 kBMlocked:              48 kBSwapTotal:      25137148 kBSwapFree:       25137148 kBDirty:                72 kBWriteback:             0 kBAnonPages:       2024884 kBMapped:           426756 kBShmem:             74552 kBSlab:             170052 kBSReclaimable:     120684 kBSUnreclaim:        49368 kBKernelStack:       11760 kBPageTables:        48856 kBNFS_Unstable:          0 kBBounce:                0 kBWritebackTmp:          0 kBCommitLimit:    37467408 kBCommitted_AS:    8069992 kBVmallocTotal:   34359738367 kBVmallocUsed:           0 kBVmallocChunk:          0 kBHardwareCorrupted:     0 kBAnonHugePages:    397312 kBCmaTotal:              0 kBCmaFree:               0 kBHugePages_Total:       0HugePages_Free:        0HugePages_Rsvd:        0HugePages_Surp:        0Hugepagesize:       2048 kBDirectMap4k:      277632 kBDirectMap2M:     7032832 kBDirectMap1G:    19922944 kBfree -m              total        used        free      shared  buff/cache        availableMem:          24082        2263       20553          68        1264       21364Swap:         24547           0       24547
Ubuntu 16.04 only recognizes 24GB RAM out of 32GB
hardware;ram