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

[Dimitry Andric]

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.
> 
> 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.

Another option is to try PAE, but I have no idea how stable that is...

-Dimitry

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