Graphics Fan-out Switch

The number and variety of PCI Express native-mode devices

is growing quickly. The devices such as graphics cards are

expected to become mainstream very rapidly. As that happens,

it will be necessary to take a wide (x16) graphics port on the

root complex device and fan it out to four x4 or two x8 ports.

Figure 3. Graphics Fan-out

Dual Host Model

The ExpressLane PEX 8532 supports applications requiring

dual host, host failover, and load-sharing applications

through the non-transparency feature. Figure 4 illustrates a

dual host system using an intelligent adapter card.

Figure 4. Dual Host Usage

In this figure, the primary CPU (on the right) is the active

host; it configures and enumerates the system, and handles

interrupts and error conditions. If the primary host ceases

proper operation, the secondary host takes over the system.

The PEX 8532 can dynamically re-assign both the upstream

port (from primary to secondary) and the non-transparent

port (from the secondary to the primary), and allow the system

to continue operation.

Dual Fabric Model

High performance communications, storage, and blade

server systems often require more reliability than a single host

system provides. For these high availability systems, all

single points of failure must be eliminated. The ExpressLane

PEX 8532 can offer this additional level of redundancy by

linking together 2 switch fabric cards in a dual-star topology.

Figure 5 shows an example of such a system. In this system,

both the host and fabric are on separate cards, and both can be

active simultaneously. The unique non-transparency feature

of the PEX 8532 is used to allow one fabric/host card to be the

primary and the other to be the secondary.

This approach can be used to provide more than two active

processing nodes. It is straightforward to create a generalized

multiprocessor system with smaller ExpressLane switches on

each card in non-transparent mode, and several PEX 8532

fabric cards to provide the fabric backbone.

Figure 5. Dual Host & Fabric Usage

Switch Fabric Module

The ExpressLane PEX 8532 can also be used in Blade Server

switch fabric applications. Figure 6 illustrate the use of PEX

8532 in a Benes Switch configuration. The non-transparency

and peer-to-peer functions of PEX 8532 enable use of fewer

total switching elements and less hops from source to

destination.

Figure 6. Benes Switch Fabric