GA-X48-DS5 Overclock problem --- Malfunction of Fine CPU Clock ratio

I was disappointed by the overclock performance of Gigabyte X48 motherboard, my system information are as following:

CPU: Intel Q9450 (Default 333Mhz x 8 = 2.66GHZ)
Main board: GA-X48-DS5 revision 1.1 BIOS F5 & F6b
BIOS setting For 3.4Ghz overclocking
In the MB Intelligent Tweaker screen, set:
Robus graphics booster: standard
CPU clock ratio: 8x
Fine CPU Clock ratio: +0.5x
cpu host clock control: enable
cpu host clock frequency: 400
PCI Express frequency: 100
C.I.A.2: disable
Performance Enhance: standard
System memory multiplier: [2.00D]
Dram Timing Selectable: Manual
Standard Timing control:
6
6
6
18
System voltage control: manual
DDR2
Overvoltage: +0.2V from original 1.8volts.
Loadline Calibration: Enable
CPU Voltage Control: 1.25V
All others remain at default / normal.

Stress Test by Super Pi 32M and 16M together are OK.

Everything looks good but after I boot into the Windows XP SP2, I found the CPU speed is only 3.2GHZ where it is 400Mhz x 8, in other word it means the Fine CPU clock ration [+0.5] is malfunction. Right now I use HD3870 of 3DMark06 with 12992 at default setting (1280x1024) and 10215 for resolution 1920x1200, however I concerned Q9450 of only 3.2GHZ maybe a bit of bottleneck if I change my display card to HD4870 once it is available in market.

Is there any hardware expert can help me. Thanks for a lot.