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DateMon, 16 May 2005 13:48:23 -0400
FromBrian Gerst <>
SubjectRe: I'm having 4GB RAM, but Linux sees just 3GB???
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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