Dual core CPU's, but only 2 CPU's in-use?

[Tigger]

Hello. I have a Xeon system with 2 CPU's installed (dual-cores). Under
FreeBSD 6.2, a systat reported 4 CPUs in use and so did dmesg. 

Under FreeBSD 6.3, dmesg is reporting the 4 CPUs, but systat is only
reporting 2 CPUs (CPU 0 and CPU 2). 

How do I enabled the second cores on the CPU's or are they really
running but systat is not reporting the CPU load across the cores?

dmesg from 6.3 (snipped):
CPU: Intel(R) Xeon(TM) CPU 2.80GHz (2790.73-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
  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=0x4400<CNXT-ID,xTPR>
  Logical CPUs per core: 2
real memory  = 2147352576 (2047 MB)
avail memory = 2096242688 (1999 MB)
ACPI APIC Table: <DELL   PE1600SC>
FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1
 cpu2 (AP): APIC ID:  6
 cpu3 (AP): APIC ID:  7

And sysctrl dev.cpu is interesting, the 4 CPUs are found but only 2
appear to be working (cx_usage is 100% or 0%):

# sysctl dev.cpu
dev.cpu.0.%desc: ACPI CPU
dev.cpu.0.%driver: cpu
dev.cpu.0.%location: handle=\_PR_.CPU0
dev.cpu.0.%pnpinfo: _HID=none _UID=0
dev.cpu.0.%parent: acpi0
dev.cpu.0.cx_supported: C1/0
dev.cpu.0.cx_lowest: C1
dev.cpu.0.cx_usage: 100.00%
dev.cpu.1.%desc: ACPI CPU
dev.cpu.1.%driver: cpu
dev.cpu.1.%location: handle=\_PR_.CPU1
dev.cpu.1.%pnpinfo: _HID=none _UID=0
dev.cpu.1.%parent: acpi0
dev.cpu.1.cx_supported: C1/0
dev.cpu.1.cx_lowest: C1
dev.cpu.1.cx_usage: 0%
dev.cpu.2.%desc: ACPI CPU
dev.cpu.2.%driver: cpu
dev.cpu.2.%location: handle=\_PR_.CPU2
dev.cpu.2.%pnpinfo: _HID=none _UID=0
dev.cpu.2.%parent: acpi0
dev.cpu.2.cx_supported: C1/0
dev.cpu.2.cx_lowest: C1
dev.cpu.2.cx_usage: 100.00%
dev.cpu.3.%desc: ACPI CPU
dev.cpu.3.%driver: cpu
dev.cpu.3.%location: handle=\_PR_.CPU3
dev.cpu.3.%pnpinfo: _HID=none _UID=0
dev.cpu.3.%parent: acpi0
dev.cpu.3.cx_supported: C1/0
dev.cpu.3.cx_lowest: C1
dev.cpu.3.cx_usage: 0%

Thanks for any pointers on this one!

-Tig