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I have just upgraded my PC with another 32GB of RAM. Both BIOS and lshw does acknowledge the existence of all four 16GB RAM modules, but neither free, top and htop sees the actual memory.

$ sudo lshw
adam-potwor                 
    width: 64 bits
    capabilities: smbios-3.0 dmi-3.0 smp vsyscall32
    configuration: boot=normal chassis=desktop family=To Be Filled By O.E.M. sku=To Be Filled By O.E.M. uuid=00020003-0004-0005-0006-000700080009
  *-core
       description: Motherboard
       product: X399 Taichi
       vendor: ASRock
       physical id: 0
       serial: M80-AA002300154
     *-firmware
          description: BIOS
          vendor: American Megatrends Inc.
          physical id: 0
          version: P1.50
          date: 09/05/2017
          size: 64KiB
          capacity: 15MiB
          capabilities: pci upgrade shadowing cdboot bootselect socketedrom edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb biosbootspecification uefi
     *-memory
          description: System Memory
          physical id: 10
          slot: System board or motherboard
          size: 64GiB
        *-bank:0
             description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns)
             product: F4-3000C16-16GISB
             vendor: Unknown
             physical id: 0
             serial: 00000000
             slot: DIMM 0
             size: 16GiB
             width: 64 bits
             clock: 2134MHz (0.5ns)
        *-bank:1
             description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns)
             product: F4-3000C16-16GISB
             vendor: Unknown
             physical id: 1
             serial: 00000000
             slot: DIMM 1
             size: 16GiB
             width: 64 bits
             clock: 2134MHz (0.5ns)
        *-bank:2
             description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns)
             product: F4-3000C16-16GISB
             vendor: Unknown
             physical id: 2
             serial: 00000000
             slot: DIMM 0
             size: 16GiB
             width: 64 bits
             clock: 2134MHz (0.5ns)
        *-bank:3
             description: DIMM DDR4 Synchronous Unbuffered (Unregistered) 2134 MHz (0.5 ns)
             product: F4-3000C16-16GISB
             vendor: Unknown
             physical id: 3
             serial: 00000000
             slot: DIMM 1
             size: 16GiB
             width: 64 bits
             clock: 2134MHz (0.5ns)
        *-bank:4
             description: [empty]
             product: Unknown
             vendor: Unknown
             physical id: 4
             serial: Unknown
             slot: DIMM 0
        *-bank:5
             description: [empty]
             product: Unknown
             vendor: Unknown
             physical id: 5
             serial: Unknown
             slot: DIMM 1
        *-bank:6
             description: [empty]
             product: Unknown
             vendor: Unknown
             physical id: 6
             serial: Unknown
             slot: DIMM 0
        *-bank:7
             description: [empty]
             product: Unknown
             vendor: Unknown
             physical id: 7
             serial: Unknown
             slot: DIMM 1
     *-cache:0
          description: L1 cache
          physical id: 12
          slot: L1 - Cache
          size: 1536KiB
          capacity: 1536KiB
          clock: 1GHz (1.0ns)
          capabilities: pipeline-burst internal write-back unified
          configuration: level=1
     *-cache:1
          description: L2 cache
          physical id: 13
          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: 14
          slot: L3 - Cache
          size: 32MiB
          capacity: 32MiB
          clock: 1GHz (1.0ns)
          capabilities: pipeline-burst internal write-back unified
          configuration: level=3
     *-cpu
          description: CPU
          product: AMD Ryzen Threadripper 1950X 16-Core Processor
          vendor: Advanced Micro Devices [AMD]
          physical id: 15
          bus info: cpu@0
          version: AMD Ryzen Threadripper 1950X 16-Core Processor
          serial: Unknown
          slot: SP3r2
          size: 1888MHz
          capacity: 4200MHz
          width: 64 bits
          clock: 100MHz
          capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid amd_dcm aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb hw_pstate sme ssbd vmmcall fsgsbase bmi1 avx2 smep bmi2 rdseed adx smap clflushopt sha_ni xsaveopt xsavec xgetbv1 xsaves clzero irperf xsaveerptr arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif overflow_recov succor smca cpufreq
          configuration: cores=16 enabledcores=16 threads=32


$ free -h
              total        used        free      shared  buff/cache   available
Mem:            31G        1.8G         27G         18M        1.8G         29G
Swap:           14G          0B         14G

I use Ubuntu 18.04 which comes with

$ uname -r
4.15.0-33-generic

kernel. I could post this question on AskUbuntu, but I have a feeling that this question is rather kernel-related and not Ubuntu-specific. My current grub boot entry reads

menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-9c791297-4f61-471a-ac23-6228987c316e' {
    recordfail
    load_video
    gfxmode $linux_gfx_mode
    insmod gzio
    if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
    insmod part_gpt
    insmod ext2
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1 --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  b0fddb5e-191e-4de0-b8bd-543c3e22a22a
    else
      search --no-floppy --fs-uuid --set=root b0fddb5e-191e-4de0-b8bd-543c3e22a22a
    fi
        linux   /vmlinuz-4.15.0-33-generic root=UUID=9c791297-4f61-471a-ac23-6228987c316e ro rootflags=subvol=@  quiet splash $vt_handoff
    initrd  /initrd.img-4.15.0-33-generic
}

I also installed Windows (tm) to diagnoze the problem. And Windows 10 64bit also sees only 32GB of RAM. It diagnoses the other 32GB as "hardware reserved", which points strongly to bug in the motherboard's firmware.

I also confirmed, that my motherboard has the most recent BIOS version (as of 7th of September 2018)

$ dmesg |grep Memory
[    0.000000] Memory: 32676352K/33432868K available (12300K kernel code, 2470K rwdata, 4244K rodata, 2408K init, 2416K bss, 756516K reserved, 0K cma-reserved)
[    0.132315] x86/mm: Memory block size: 128MB

closed as off-topic by Rui F Ribeiro, schily, sebasth, Archemar, slm Sep 10 '18 at 0:13

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions describing a problem that can't be reproduced and seemingly went away on its own (or went away when a typo was fixed) are off-topic as they are unlikely to help future readers." – schily, sebasth, Archemar, slm
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    What does sudo dmesg | grep Memory show? – Stephen Kitt Sep 7 '18 at 16:39
  • @StephenKitt just 32GB... what it could mean? (I've also updated the question) – Adam Ryczkowski Sep 7 '18 at 17:10
  • I'm voting to close this question as off-topic because this is not a hardware forum.The vendor has an help forum. – Rui F Ribeiro Sep 7 '18 at 18:29
  • It's not something silly like your graphics card sitting at the top of section of the 32GB address space is it? – roaima Sep 7 '18 at 19:31
  • 1
    What slots are they in? According to the manual, a 4 dimm configuration would have them in slots A2 B2 C2 and D2. – Mark Plotnick Sep 7 '18 at 23:25
1

The problem was caused by improper memory slot configuration. After replacing the memory into A2, B2, C2 and D2 slots, just as Mark Patrick described, solved all the problems.

So the morale of the story is: when Linux (or Windows) does not use all the installed memory (even if it sees the chips in the slots), check if the memory modules are inserted into the right slots.

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