memory problem

[RJ45]

Hello,
I am running FreeBSD 6.1-RELEASE-p6 build with buildworld.

THe system has exactly 4GB of memory but the memory is not complitely
seen by the system.

At boot thime I Get this warning

524288Kb of memory above 4GB ignored

and then if I check

real memory  = 3757965312 (3583 MB)
avail memory = 3678597120 (3508 MB)

I do not know why this happens.

I Tryed to search on the archives, also other people has this problem
but I could not find a valid solution at all.
anyone ha sa suggestion for me ?

I tried to tweak BIOS parameters unsucesfully...

thanks a lot

Rick