System for providing bridging of backplane

Details System for providing bridging of backplane System for providing bridging of backplane

1998-11-10

2001-08-28

Dharia, Rupal (Department: 2181)

Electrical computers and digital data processing systems: input/

Intrasystem connection

Bus access regulation

C710S108000, C710S120000, C710S120000, C710S009000

Reexamination Certificate

active

06282599

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to backplane expansion slot configurations, and more particularly to a backplane expansion slot configuration allowing for efficient bridging and extension of expansion slot buses when combining systems in a single cabinet.
BACKGROUND OF THE INVENTION
Various implementations have been made in the industry to extend the bus architecture of computer systems to additional chassis. This was first widely implemented in the early 1980's as PC expansion chassis were commercialized by IBM and others. These systems extended the processor bus by inserting a card in one processor slot of each system and then interconnecting the systems by a cabling configuration between the inserted cards. This solution was satisfactory with the relatively slow systems of the time. A more recent example is Dialogic Corporation's ScxBus extender. This implementation takes signals from a time division multiplexed bus and retransmits them over a SCSI-like cable and connector system. This system is very costly and the distance the system can be extended is limited due to timing and loss considerations. Cabling approaches such as these that connect separate chassis or slot sets in a cabinet disrupt the timing and electrical characteristics of the resultant extended bus.
A system's capabilities can also be extended by transmitting bus information to another system's bus over a LAN using protocols such as Ethernet, ATM, or other packet protocol technologies. This also is an expensive solution, and introduces relatively long delays in the bus traffic.
Another solution to expanding an existing system within a cabinet is to replace the backplane with one that has sufficient slots for the application at hand. Not only is this solution expensive, but it is labor intensive and tends to be disruptive to the system.
Accordingly, it is an object of the present invention to provide an inexpensive solution to easily extend the expansion slots and buses of a system within a cabinet while minimizing the impact to system timing and electrical characteristics.
Another object of the present invention is to extend the expansion slots and buses of a system within a cabinet without modification or replacement of the backplane.
SUMMARY OF THE INVENTION
The present invention is a slot configuration and a bridging apparatus for expanding the expansion slots of one system to include the expansion slots of an adjacent electrically separate system within the same cabinet and bridging the system buses. The cabinet configuration of the invention allows for easy bridging of the slot sets and buses with minimal change of electrical characteristics, particularly impedance, across the bridge.
Adjacent slot sets are configured to allow for the largest combined set of contiguous expansion slots and the longest bus spans, and the adjacent end slots of the slot sets are configured so that their center-to-center spacing complies with the linear topology for slot spacing of the applicable standard.
For example, in a cabinet containing two similar but separate processor systems and a single backplane bus, the slots would be configured so that the two power supplies are in the outermost slots, the processor boards occupy the next inner slots, and the expansion slots occupy the remaining innermost slots. The expanding slots would be configured so that the expansion buses span contiguous slots and the buses include the innermost end slots. The center-to-center spacing of the adjacent innermost end expansion slots for each system is equal to the center-to-center spacing of the expansion slots within each system. With the cabinet configured in this manner, the two systems are electrically separate from each other. To expand one of the systems, the CPU and expansion cards of the other system are removed from the cabinet, a double-wide bridge card is inserted across the two adjacent innermost end expansion slots, and additional expansion cards are inserted into the vacated expansion slots as required. The resulting combined system will have the longest backplane bus possible within the cabinet, and the spacing of the bridged innermost end expansion slots assures a minimal system impact from timing and impedance characteristics across the bridge.
In general, if the cabinet contains two separate processor systems with multiple backplane buses, the slots are configured in a mirrored arrangement about the center slots with respect to bus connections. The power supplies and other non-bus cards occupy the outermost cabinet slots. The remaining expansion slots are arranged so that the expansion buses span contiguous slots and the buses include the innermost end slots. In this configuration, when the PCI bridge card is inserted across the two innermost end expansion slots, all buses will be extended with the greatest uninterrupted backplane spans.
With certain complex arrangements of multiple buses, it may not be possible for all buses to have an uninterrupted span across the backplane.


REFERENCES:
patent: 5572688 (1996-11-01), Sytwu
patent: 5781747 (1998-07-01), Smith et al.
patent: 6044411 (2000-03-01), Berglund et al.

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