Referring to
When the first type of PCI connector is mounted on the first connector pad 24, the resistors R are removed from the areas 30 thereby disconnecting the second transmission lines 29 from the first transmission lines 28. The removal of the switches makes a segment of each of the first transmission lines 28 that connect the first connector pad 24 to the area 30 a stub. In order to avoid signal reflection because of impedance mismatching, the length of the segment of the first transmission line 28 must satisfy the following formula:
L
stub<(Tj*V)/2
When the second type of PCI connector is mounted on the second connector pad 26, the first connector pad 24 is idle, the resistors R are mounted on the areas 30 to connect the second transmission lines 29 to the first transmission lines 28, thus the chipset 22 can communicate with the second connector mounted on the second connector pad 26.
The resistance of the resistor R is preferably zero Ohms. Alternatively, the zero Ohm resistor can be replaced by a jumper. The function of the resistor in this embodiment is as a switch, when the second connector is mounted on the motherboard the switch is turned on by placement of the resistor, when the first connector is mounted on the motherboard the switch is turned off by removal of the resistor.
A capacitor (not shown) can be connected in the first transmission line 28 to filter signal noise.
The chipset 22 can be a north bridge chipset, the first PCI connector can be a PCI-express×8 connector, and the second PCI connector can be a PCI-express×4 connector.
Thus, the motherboard is capable of flexibly supporting different PCI-express connectors using one layout, and signal integrity is maintained, and the cost for designing and producing motherboards is reduced.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
---|---|---|---|
200610062436.9 | Sep 2006 | CN | national |