Date: Sun, 28 Jan 2018 10:32:44 -0600 From: Mike Karels <mike@karels.net> To: Dimitry Andric <dim@FreeBSD.org> Cc: Andre Albsmeier <Andre.Albsmeier@siemens.com>, freebsd-stable@freebsd.org Subject: Re: i386 with 4GB RAM: less than 2GB available on A2SAV (Intel Atom E3940) Message-ID: <201801281632.w0SGWiui055204@mail.karels.net> In-Reply-To: Your message of Sun, 28 Jan 2018 17:05:54 %2B0100. <FF56490E-BD56-4BF1-B1D7-866ACEB32DC4@FreeBSD.org>
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> 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. > >=20 > > 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: > >=20 > > FreeBSD 11.1-STABLE #0: Mon Jan 15 06:57:10 CET 2018 > > ... > > real memory =3D 4294967296 (4096 MB) > > avail memory =3D 1939558400 (1849 MB) > > ... > >=20 > > 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. > Another option is to try PAE, but I have no idea how stable that is... > -Dimitry I suspect that the unavailable RAM has been mapped above 4 GB by the BIOS. About PAE: at $JOB, we have a FreeBSD 8.2 system that has been running PAE reliably since 8.2 was new. Also, we ship amd64 systems that run mostly 32-bit binaries, which works well. Mike
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