The competition only available for those who bought the earlier chipset, before B3.
Please consider to buy 1st as you get to join the competition  + get SATA 6Gbps card ma.
Dear yinchet,
Sorry to missed out your question.
To identify B3 chipset motherboards, MSI will be renaming all the new SandyBridge motherboards with (B3) attached to the original models. Please refer to the example below:

Sticker on the motherboard to show new B3 stepping motherboard.


The product code sticker on the box will show (B3) at the end.


at the front of the motherboard where the product name is will shown (B3) as well.


The serial number sticker at the back of the motherboard will show (B3) as well.


Or you can download our MSI 6 Series Sata Scan Program to check whether if it's the B3 stepping you got.

More information can be found here:SandyBridge Chipset (B2/B3) Identification of MSI’s 6 Series Mainboards

Thank you.