Asus P5k Primary PCI Express x16 slot, Universal PCI-Eslot (max. x4 mode), PCI Express operating speed

We recommend that you install a VGA card on the primary (blue) PCI Express slot, and install any other PCI Express device on the Universal PCI-E slot (black).

Primary PCI Express x16 slot

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

Universal PCI-E slot (max. x4 mode)

This motherboard also supports a Universal PCI-E 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.

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 2-34 for the connector location.

Options for Universal PCI Express slot	PCI Express operating speed
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