Hi,

i have ASRock X58 Supercomputer mobo, which supports 24GB , DDR3. I have 6 DIMMs (each of 4GB) installed, i can see them all recognized in BIOS menu. However when i boot Linux kernel 2.6.28 (Gentoo R5) only 12GB are recognized. I tried mem=24GB on boot, but no luck. What could it be?
Could it be the page size? Or maybe because i only have 4GB swap ? Tried 2.6.30 kernel , no luck either.

Thanks in advance.

Attached is the dmesg output for ram maping:

[ 0.000000] BIOS EBDA/lowmem at: 0009b800/0009b800
[ 0.000000] Initializing cgroup subsys cpuset
[ 0.000000] Initializing cgroup subsys cpu
[ 0.000000] Linux version 2.6.28-gentoo-r5 (root@master) (gcc version 4.3.2 (Gentoo 4.3.2-r3 p1.6, pie-10.1.5) ) #4 SMP
Tue May 26 11:27:16 Local time zone must be set--see zic
[ 0.000000] Command line: root=/dev/sda2 mem=24GB
[ 0.000000] KERNEL supported cpus:
[ 0.000000] Intel GenuineIntel
[ 0.000000] AMD AuthenticAMD
[ 0.000000] Centaur CentaurHauls
[ 0.000000] BIOS-provided physical RAM map:
[ 0.000000] BIOS-e820: 0000000000000000 - 000000000009b800 (usable)
[ 0.000000] BIOS-e820: 000000000009b800 - 00000000000a0000 (reserved)
[ 0.000000] BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved)
[ 0.000000] BIOS-e820: 0000000000100000 - 00000000bbe90000 (usable)
[ 0.000000] BIOS-e820: 00000000bbe90000 - 00000000bbea0000 (ACPI data)
[ 0.000000] BIOS-e820: 00000000bbea0000 - 00000000bbed0000 (ACPI NVS)
[ 0.000000] BIOS-e820: 00000000bbed0000 - 00000000bbee0000 (reserved)
[ 0.000000] BIOS-e820: 00000000bbeeb800 - 00000000bc000000 (reserved)
[ 0.000000] BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
[ 0.000000] BIOS-e820: 00000000ffb00000 - 0000000100000000 (reserved)
[ 0.000000] BIOS-e820: 0000000100000000 - 0000000344000000 (usable)
[ 0.000000] user-defined physical RAM map:
[ 0.000000] user: 0000000000000000 - 000000000009b800 (usable)
[ 0.000000] user: 000000000009b800 - 00000000000a0000 (reserved)
[ 0.000000] user: 00000000000e4000 - 0000000000100000 (reserved)
[ 0.000000] user: 0000000000100000 - 00000000bbe90000 (usable)
[ 0.000000] user: 00000000bbe90000 - 00000000bbea0000 (ACPI data)
[ 0.000000] user: 00000000bbea0000 - 00000000bbed0000 (ACPI NVS)
[ 0.000000] user: 00000000bbed0000 - 00000000bbee0000 (reserved)
[ 0.000000] user: 00000000bbeeb800 - 00000000bc000000 (reserved)
[ 0.000000] user: 00000000fee00000 - 00000000fee01000 (reserved)
[ 0.000000] user: 00000000ffb00000 - 0000000100000000 (reserved)
[ 0.000000] user: 0000000100000000 - 0000000344000000 (usable)
[ 0.000000] DMI present.
[ 0.000000] AMI BIOS detected: BIOS may corrupt low RAM, working it around.
[ 0.000000] last_pfn = 0x344000 max_arch_pfn = 0x3ffffffff
[ 0.000000] x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106
[ 0.000000] last_pfn = 0xbbe90 max_arch_pfn = 0x3ffffffff
[ 0.000000] init_memory_mapping: 0000000000000000-00000000bbe90000
[ 0.000000] 0000000000 - 00bbe00000 page 2M
[ 0.000000] 00bbe00000 - 00bbe90000 page 4k
[ 0.000000] kernel direct mapping tables up to bbe90000 @ 10000-15000
[ 0.000000] last_map_addr: bbe90000 end: bbe90000
[ 0.000000] init_memory_mapping: 0000000100000000-0000000344000000
[ 0.000000] 0100000000 - 0344000000 page 2M
[ 0.000000] kernel direct mapping tables up to 344000000 @ 13000-22000
[ 0.000000] last_map_addr: 344000000 end: 344000000

The Linux kernel is not as advanced as the NT kernel is ...
so a high amount of ram that is recognized by windows, may not be by linux.

Why do you need such a high amount of RAM ??.

in linux, just one 4Gb stick of memory should be more than enough.

( or are you "just experimenting" )

your swap file needs to be only about 1Gb, max.
or, even zero.. with about that much memory ( ~4Gb)

That's going to get a lot of argument here!!

Never heard this before....If you have a 64-bit processor and a current OS, why would Linux not be able to access as much RAM as Windows? Do you have any links that discuss this?

I think this duplicate thread was already resolved at
http://www.linuxquestions.org/questi...92#post3598392

Is that the nonsense it appears to be, or do you have some facts?

I know of a bunch of situations in which Linux will recognize more physical ram than Windows will (generally license restrictions, not technical restrictions, but to the end user only the results matter).

I don't know any cases of the reverse.

Why do you assume he doesn't?

Computers are occasionally used for tasks more demanding than surfing the net.

That depends on what the computer will be used for.

This does not make sense. The NT kernel supports 2TB of RAM on x86-64. Linux supports 64TB of RAM on x86-64. Moreover, on other archs with full 64-bit processors, such as sparc, powerpc, ia64, s390, parisc, etc., linux puts fewer/no software restrictions (i.e., if the hardware supports 16EB, so will linux).

It seems this is the case. The NT kernel can support 2TB of ram, yet Vista has limited this to anywhere from 8BG to 128GB depending on what license you get.

Hi, maybe it's a stupid question but just want to be sure: Your kernel is compiled as x86_64 (amd64) architecture, not x86 (32bit)?