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

[Brian Gerst <bgerst@didntduck.org>]

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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