Arch Linux

Gaen

Member

Registered: 2020-12-16

Posts: 28

[SOLVED] RAM size not recognized correctly

Hi,

I recently noticed that not all of the installed RAM is being detected.
Other operating systems and BIOS recognize it correctly.

OS:         Arch Linux 
Kernel:     x86_64 Linux 5.10.16-arch1-1
Bootloader: GRUB
System:     BIOS
DE:         KDE 5.79.0 / Plasma 5.20.5
WM:         KWin
RAM:        1883MiB / 3928MiB           // 4096MiB in real



sudo lshw | grep -A 8 "bank"
---------------------------
        *-bank:0            
             description: DIMM SDRAM Synchronous 800 MHz (1,2 ns)
             product: ModulePartNumber00
             vendor: Manufacturer00
             physical id: 0
             serial: SerNum00
             slot: DIMM1
             size: 2GiB
             width: 64 bits
--
        *-bank:1
             description: DIMM SDRAM Synchronous 800 MHz (1,2 ns)
             product: ModulePartNumber01
             vendor: Manufacturer01
             physical id: 1
             serial: SerNum01
             slot: DIMM2
             size: 2GiB
             width: 64 bits



sudo dmidecode | grep -A 7 "Memory Module Information"
------------------------------------------------------
Memory Module Information
        Socket Designation: DIMM1
        Bank Connections: 0 1
        Current Speed: Unknown
        Type: DIMM SDRAM
        Installed Size: 2048 MB (Double-bank Connection)
        Enabled Size: 2048 MB (Double-bank Connection)
        Error Status: OK
--
Memory Module Information
        Socket Designation: DIMM2
        Bank Connections: 4 5
        Current Speed: Unknown
        Type: DIMM SDRAM
        Installed Size: 2048 MB (Double-bank Connection)
        Enabled Size: 2048 MB (Double-bank Connection)
        Error Status: OK



free -m
--------
              total        used        free      shared  buff/cache   available
Mem:           3928         928        2300          11         699        2768
Swap:          8191           0        8191



free -h
--------
              total        used        free      shared  buff/cache   available
Mem:          3,8Gi       927Mi       2,2Gi        11Mi       699Mi       2,7Gi
Swap:         8,0Gi          0B       8,0Gi

Changed the kernel parameters, re-generated the grub.cfg and rebooted the system.

sudo vim /etc/default/grub

    GRUB_CMDLINE_LINUX_DEFAULT="... mem=4096M"

sudo grub-mkconfig -o /boot/grub/grub.cfg

reboot

Then it ended up with 2985MB, so I reverted these changes back.. What causes this?

Last edited by Gaen (2021-02-21 19:20:37)

loqs

Member

Registered: 2014-03-06

Posts: 18,917

Re: [SOLVED] RAM size not recognized correctly

4096-3928=168 Is that the amount you are looking to find?  Check dmesg for reserved ranges.

Gaen

Member

Registered: 2020-12-16

Posts: 28

Re: [SOLVED] RAM size not recognized correctly

I thought only integrated GPUs use reserved memory, thanks for the clarification!

Last edited by Gaen (2021-03-14 20:43:33)