Asus P8B-X - Chapter 2: Hardware information; 2.1 Before you proceed; 2.2 Motherboard overview

R1.0x (Z9s) R2.0x (AST1100)
How to differentiate the motherboard
SN label location
* B means year, B=2011, C=2012… 9 means month, 1...9, A, B, C
** After September 2011, we will be shipping R2.0x, the SN will be B9S2XXXXXXXX or above