Re: I'm having 4GB RAM, but Linux sees just 3GB???

From: Brian Gerst
Date: Mon May 16 2005 - 12:48:51 EST


Christian Parpart wrote:
On Monday 16 May 2005 4:44 pm, Brian Gerst wrote:

Christian Parpart wrote:

Hi all,

I was asking this in gentoo-server mailing list before, however, they
finally pointed me to this place as it could also be a bug in the kernel.

I'm having a TYAN board with two AMD Opteron 248 and 4x 1GB ECC RAM on
it. The BIOS reflects what I've plugged in, however, the operating system
does not.

my `uname -a` output is:
Linux battousai 2.6.11-gentoo-r8 #1 SMP Sat May 14 02:42:15 CEST 2005
x86_64 AMD Opteron(tm) Processor 248 AuthenticAMD GNU/Linux

and my `dmidecode` output is located at [0]. For ANY reason, dmidecode
even knows about my 4GB RAM, but `free -m` nor `kinfocenter` of KDE
claims to see just 3GB.

free -m:
total used free shared buffers cached
Mem: 3015 2993 22 0 15 2638
-/+ buffers/cache: 338 2677
Swap: 511 1 510

This is rather sad to see 1GB RAM plugged in for nothing.

Has anyone a hint for my WHY this is happening and HOW I could get rid of
it?

Thanks in advance,
Christian Parpart.

[0] http://dev.gentoo.org/~trapni/dmidecode.txt

Are you running a 64-bit kernel? What does "dmesg | grep e820" show?


BIOS-e820: 0000000000000000 - 0000000000094800 (usable)
BIOS-e820: 0000000000094800 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000c2000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000bff20000 (usable)
BIOS-e820: 00000000bff20000 - 00000000bff2e000 (ACPI data)
BIOS-e820: 00000000bff2e000 - 00000000bff80000 (ACPI NVS)
BIOS-e820: 00000000bff80000 - 00000000c0000000 (reserved)
BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
BIOS-e820: 00000000fec00000 - 00000000fec00400 (reserved)
BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
BIOS-e820: 00000000fff80000 - 0000000100000000 (reserved)

hmm... what does this mean?

It means that there is a hole at 00000000c0000000 - 0000000100000000 (3GB-4GB) for PCI memory-mapped devices. The 4th GB of RAM should be remapped by the BIOS to 4GB-5GB, but isn't. Your BIOS is either buggy or misconfigured.

--
Brian Gerst
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