I had to search a while to find this pinout, so I might as well post it so someone else can find it — although I have a feeling that I’ll be the one that needs it again.
Copy of correct pinout
DB-9 IDC-10 Pin 1 Pin 1 Pin 2 Pin 2 Pin 3 Pin 3 Pin 4 Pin 4 Pin 5 Pin 5 Pin 6 Pin 6 Pin 7 Pin 7 Pin 8 Pin 8 Pin 9 Pin 9
The pin-out for the serial connector on the motherboard is incorrect in the some manuals. In fact it is incorrect in the latest English version dated September 2008 on the ASUS website. The correct pin-out is:
_______ |2468X| |13579| --- ---
Thanks to Andreas for his help establishing this.