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

[Eric van Gyzen]

On 01/28/2018 10:05, Dimitry Andric wrote:
> 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.

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

Eric