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[SOLVED] 64 bit kernel sees only 3GB of memory
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fargred
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PostPosted: Fri Apr 29, 2016 1:53 am    Post subject: [SOLVED] 64 bit kernel sees only 3GB of memory Reply with quote

It’s Lenovo Ideapad flex 10, BIOS reports all 4 GB are in place.
But
Code:
# lshw -c memory
  *-memory               
       description: System memory
       physical id: 0
       size: 2888MiB
# free -m
              total        used        free      shared  buff/cache   available
Mem:           2888          22        2808           0          58        2832
Swap:          4095           0        4095
I understand, that some memory may go to the integrated graphics, but it steals only 0xbeffffff-0xbb000000 which equals to something around 64M is I still remember how to count.
Code:
# dmesg | egrep '(Mem|raph)'
[    0.000000] Reserving Intel graphics stolen memory at 0xbb000000-0xbeffffff
[    0.000000] Memory: 2913596K/3026136K available (6931K kernel code, 967K rwdata, 2780K rodata, 972K init, 584K bss, 112540K reserved, 0K cma-reserved)
[    0.478578] [drm] Memory usable by graphics device = 2048M
The kernel is definitely 64 bit
Code:
# zgrep -i 64bit /proc/config.gz
CONFIG_64BIT=y
so no PAE should be needed.

Last edited by fargred on Fri Apr 29, 2016 2:00 am; edited 1 time in total
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1clue
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PostPosted: Fri Apr 29, 2016 1:56 am    Post subject: Reply with quote

Check your bios. Some computers have a 32-bit compatibility mode that reports 3g or so to the os.

This is independent of what the bios reports. Bios will tell you what it sees, but will report less to the os.
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fargred
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PostPosted: Fri Apr 29, 2016 2:00 am    Post subject: Reply with quote

1clue wrote:
Check your bios. Some computers have a 32-bit compatibility mode that reports 3g or so to the os.

This is independent of what the bios reports. Bios will tell you what it sees, but will report less to the os.

Yep, this is it. Thank you, I wouldn’t even think that ‘legacy boot’ assumes ‘hurr we x86 nao’.
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1clue
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PostPosted: Fri Apr 29, 2016 2:23 am    Post subject: Reply with quote

I would have thought this would have gone away years ago, but my year-old 8-core uefi-capable setup with up to 64g ram has this mode. It doesn't even accept a memory configuration that small. So technically you would have to put 16g in it (minimum config) and then tell the OS you have 3g? Why would anyone do that?
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