Asus P5K/EPU manual Primary PCI Express x16 slot, Universal PCI Express slot max. x4 mode

Primary PCI Express x16 slot

The primary PCI Express x16 slot supports PCI Express x16 graphic cards that comply with the PCI Express specifications.

Universal PCI Express slot (max. x4 mode)

This motherboard also supports a Universal PCI Express slot with a maximum speed of 2 GB/s. The operating frequency of this slot changes, depending on the type of PCI Express card you install. Refer to the table below for details.

The figure shows two graphics cards installed on the primary PCI Express x16 slot and the Universal PCI Express slot.

If you install two VGA cards, we recommend that you plug the rear chassis fan cable to the motherboard connector labeled CHA_FAN1 for better thermal environment. See page 2-30 for the connector location.

Options for Universal PCI Express operating speed

PCI Express slot

Auto

Automatically optimizes performance and functionality according to devices installed

x4 mode [fast]

User gets the best performance but this mode disables the PCI Express x1 slot

x1 mode [compatible]

Always runs at PCI Express x1 speed

•Some PCI Express graphics cards cannot operate on x4/x1 mode. We suggest that you install these cards on the primary PCI Express slot (blue) to increase system stability.

•Some PCI Express devices cannot operate on x4/x1 mode.

2-22 Chapter 2: Hardware information