i386 with 4GB RAM: less than 2GB available on A2SAV (Intel Atom E3940)

[Mike Karels]

> On 28 Jan 2018, at 15:57, Andre Albsmeier <Andre.Albsmeier at 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