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Date:      Mon, 29 Jan 2018 09:12:59 -0600
From:      Eric van Gyzen <eric@vangyzen.net>
To:        freebsd-stable@freebsd.org
Subject:   Re: i386 with 4GB RAM: less than 2GB available on A2SAV (Intel Atom E3940)
Message-ID:  <f430996f-2af7-d6d5-b911-69978e0ec1f5@vangyzen.net>
In-Reply-To: <FF56490E-BD56-4BF1-B1D7-866ACEB32DC4@FreeBSD.org>
References:  <20180128145703.GA80724@bali> <FF56490E-BD56-4BF1-B1D7-866ACEB32DC4@FreeBSD.org>

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On 01/28/2018 10:05, Dimitry Andric wrote:
> On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier@siemens.com> wrote:
>> I have a lot of machines running with 4 GB physical RAM and, for
>> some reasons, I still have to use a 32 bits OS.
>>
>> All of them show something between 3 and 3.5 GB of RAM available
>> in dmesg but the brand new Supermicro A2SAV really shocked me:
>>
>> FreeBSD 11.1-STABLE #0: Mon Jan 15 06:57:10 CET 2018
>> ...
>> real memory  = 4294967296 (4096 MB)
>> avail memory = 1939558400 (1849 MB)
>> ...
>>
>> So do people have any ideas how I might get a bit closer to at least
>> 3 GB? I assume there are no FreeBSD knobs which might help but hope
>> dies last...
> 
> This is a common problem on i386.  Most likely some ranges are reserved
> for I/O mappings, such as video cards.  If you boot with -v, I think the
> kernel prints an overview of the physical ram chunks available?  I don't
> know of any other way to get such an overview.

sysctl machdep.smap on BIOS, machdep.efi_map on UEFI.

Eric



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