CONFIDENTIAL
Z3-DM816X-PCI2-RPS V2.00.00
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Z3 Technology, LLC
♦
100 N 8
th
ST, STE 250
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Lincoln, NE 68508-1369 USA
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+1.402.323.0702
29
10.
PCI Express
10.1 PCIe Lanes and Slots
The Z3-DM8168-APP-41 board is designed to work with PCI Express (PCIe). The DM816X chip mounted on
the module provides a PCIe interface with 2 lanes. The PCIe specification standardizes on connectors for
1, 4, 8 and 16 lanes. The Z3-DM8168-APP-41 board is designed to mate with a 4-lane connector in order to
allow the 2 lanes from the DM8168 processor to be active.
The PCIe specification allows for plugging interface cards into any slot that provides at least as many lanes
as present on the interface card. Therefore, the Z3-DM8168-APP-41 board can fit into a slot with 4, 8, or
16 lanes.
The Z3-DM816X-PCI2-RPS board set can also operate as 1 1-lane PCIe device. This means that if the
mechanical restrictions of inserting a big board into a small slot did not exist, it would also work. Since this
is a generic situation, some motherboard vendors have included PCIe slots that have their backs open to
allow the insertion of board with more lanes than the connector. Although this
should
work well (for all
devices including the Z3-DM816X-PCI2-RPS system) there is no guarantee that it will in fact work in all
situations.
The “PCI Express Card Electromechanical Specification” section on “Card Interoperability” is a good
reference. The document is available (for members) from the PCI Group at:
http://www.pcisig.com/specifications/pciexpress/base
10.2 PCIe BIOS on the PC
When the PC is first powered up, its BIOS performs some system tests and initialization, including
initializing PCIe. The PC BIOS is required to assign resources to all peripherals in the system, including PCI
Express add-in cards, before it can boot the operating system. During this initialization, the BIOS will
determine allocation of memory addresses and interrupt lines, and use this information to turn on each
peripheral in a way that avoids conflicts.
One of the functions of the BIOS is to determine if there is a display adapter card present in the system. If
there is, the BIOS makes it the primary video monitor. Some BIOSes mistakenly think that any add-in card
present in its 16-lane PCIe slot must be a display controller, even if the PCIe card clearly tells the BIOS (via
configuration space) that it is not. This BIOS behavior is most frequent on motherboards with only one PCIe
slot or one 16-lane and one 1-lane slot, where the most popular add-in card on the 16-lane slot would in
fact be a video controller. The problem is that these systems will either not boot with the Z3-DM8168-APP-
41 card (or any other non-video card) plugged in, or boot without video. Usually there are no configuration
settings in the BIOS that will correct this behavior of the BIOS, making it effectively impossible to use that
