Asus M4A78-E - Manual (Page 40)

2-20 Chapter 2: Hardware information
Chapter 2
2.6 ASUS VGA switch card
The ASUS VGA switch card allows the Blue PCIe_x16 slot to run at full x16 mode when only
one graphics card is installed to the slot.
Installing one graphics card
When you install only one graphics card,
ensure to install the VGA switch card to the
Black PCIe x16 slot first and the graphics
card on the Blue PCIe x16 slot.
Installing two graphics cards
When you install two graphics cards,
remove the VGA switch card from the Black
PCIe x16 slot. The two x16 PCIe slots will
both run at x8 mode.
VGA configuration
PCI Express operating mode
PCIex16_2 (Blue) PCIex16_1 (Black)
Single VGA/PCIe card x16 VGA switch card installed
Dual VGA/PCIe card x8 x8