Asus Crosshair III Formula - Manual (Page 52)

• In single VGA card mode, use first the PCIe 2.0 x16_1 slot for a PCI
Express x16 graphics card to get better performance.
• In CrossFireX™ mode, use the PCIe 2.0 x16_1 and
PCIe 2.0 x16_2 (blue) slots for PCI Express x16 graphics cards to get
better performance.
• We recommend that you provide sufficient power when running
CrossFireX™ mode. See page 2-37 for details.
• Connect a chassis fan to the motherboard connector labeled
CHA_FAN1/2/3 when using multiple graphics cards for better thermal
environment.
2-24 Chapter 2: Hardware information