Well I've just downloaded the manual for the Gigabyte GA-8SIML version 1 & 2 from click here and if this is your board it looks like the 9 pin header is for a Com B connection not usb. The front usb connector is two rows of 4 pins with a gap in each row, and the two rows are wired opposite to each other, so you have 1 pin space 3 pins 3 pins space 1 pin
Which is GND, space, usb3+, usb3-, power.
power, usb2-, usb2+, space, GND
but not sure if this is the right board so check it first.