FreeBSD-6.3 only detects 3GB of RAM

Ivan Voras ivoras at
Thu Mar 27 07:35:41 PDT 2008

lhecking at wrote:
> fred writes:
>> Hello all,
>> I am trying to fix an issue with my dual xeon ibm server, it only detects
>> 3GB or RAM but I have 4GB:
> [...]
>  I have seen this problem under Linux on IBM Intellistations (6225).
>  IBM pointed me to a tech document (the number of which I do not
>  remember) that says when the machine detects more than 3GB, it uses
>  some of that memory internally for ... stuff. Still, I find stealing
>  1GB quite unacceptable.

This question is answered almost once a week. Search the archives and
you will find plenty of explanations, both long and short.

Short version: you cannot use memory near 4 GB on 32-bit operating
systems (it's a hardware limitation). You can either compile a kernel
with PAE ( or a
64-bit version of the operating system (in FreeBSD it's called AMD64
since AMD was first to create the hardware,

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