linux-kernel - Re: missing 700 MB of RAM

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Message-ID: <icep09$2hd$1@ID-44327.news.uni-berlin.de>
Date:	Mon, 22 Nov 2010 22:58:44 +0100
From:	Andreas Hartmann <andihartmann@...19freenet.de>
To:	linux-kernel@...r.kernel.org
Subject: Re: missing 700 MB of RAM

Jiri Slaby wrote:
> On 11/21/2010 08:02 PM, Andreas Hartmann wrote:
>> I've got 8 GB RAM installed, but linux reports 7,3 GB. Where is the
>> missing RAM (700 MB)?
> ...
>> The motherboard is a GA-MA78GM-S2H (64bit, AMD) with a on board Radeon
>> HD 3200 VGA card. The card uses 256 MB of RAM - so 444 MB of RAM are
>> missing. Where are they gone?
> 
> Hi, ask your BIOS:
> 
>> BIOS-provided physical RAM map:
>> BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
>> BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
>> BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
>> BIOS-e820: 0000000000100000 - 00000000afde0000 (usable)
>> BIOS-e820: 00000000afde0000 - 00000000afde3000 (ACPI NVS)
>> BIOS-e820: 00000000afde3000 - 00000000afdf0000 (ACPI data)
>> BIOS-e820: 00000000afdf0000 - 00000000afe00000 (reserved)
>> BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
>> BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
>> BIOS-e820: 0000000100000000 - 0000000230000000 (usable)
> 
> It reports 7677M of usable mem. Or maybe your loader is cheating on you?
> I doubt so...

Ok. That's right. Anyway, I'm wondering about the difference to free:

            total       used       free     shared    buffers     cached
Mem:      7706580    5271096    2435484          0      79232    3049120

which is 7526M. This means, there are missing 151M of usable RAM?!

I would have expected, that free reprots the same amount as the kernel
reports to be usable.

On the other hand, I would have expected, that the amount, reported by
free + gfx-memory should nearly be 8 GB. Here it is: 7782. Thus there
are missing 410 MB between the installed hardware and free + gfx-memory.

Does anybody kown, where to find them?


Removing the difference between free and physical ram map (410 - 151),
~259 MB are remaing. This is nearly the amount for the gfx-card, which
has already been removed. Could it be, that the gfx-memory is reserved
twice - once by the bios and another time by the kernel?!


Kind regards,
Andreas
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