From: Denis Vlasenko <vda@ilport.com.ua>
To: Christian Parpart <trapni@gentoo.org>, linux-kernel@vger.kernel.org
Subject: Re: I'm having 4GB RAM, but Linux sees just 3GB???
Date: Tue, 17 May 2005 09:34:26 +0300
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On Monday 16 May 2005 20:59, Christian Parpart wrote:
> (oops)
> 
> On Monday 16 May 2005 7:48 pm, Brian Gerst wrote:
> > >  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.
> 
> Aiiii, that's good news.
> 
> I found a "Memhole" area. But I never used to change these items. 
> Unfortunately, my TYAN board reference guide isn't telling me what to change 
> there for good - so - can you tell me where to find more information about 
> there?
> 
> If I remember correctly, it provided me the options ("Automatic"/"Manual") and 
> a value list with the following items:
> ? 64MB 128MB, 256MB, 512MB, 1024MB 2048MB, 3G, 3.5G.
> 
> and another list I can't remember by now.
> 
> but *playing* around with these values didn't help much (I just reduced my 
> memory in linux down to 2GB once but didn't find the right values for getting 
> 4GB).
> 
> So, what should I do then?

You should boot with different BIOS options and examine e820 map after
each boot, looking for setup where there is 1 Gig of RAM at 4G mark.

Also google for 'e820' to get some info on this stuff.
--
vda

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