FreeBSD-6.3 only detects 3GB of RAM

[fred]

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:


CPU: Intel(R) Xeon(TM) CPU 3.00GHz (3000.13-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf41  Stepping = 1
 
Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA
,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0x641d<SSE3,RSVD2,MON,DS_CPL,CNXT-ID,CX16,xTPR>
  AMD Features=0x20000000<LM>
  Logical CPUs per core: 2
real memory  = 3355234304 (3199 MB)
avail memory = 3278614528 (3126 MB)
ACPI APIC Table: <IBM    SERONYXP>
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs


I have read that OPTION PAE in kernel would fix the problem but I have also
read that compiling FreeBSD AMD64 might be a better solution, any advices
before I break my current setup? 

Thanks

-fred