The PEX 8508 can be used to create an adapter card that

aggregates the PCI Express devices into a single port that can

be plugged into a backplane or a motherboard. Figure 3

shows the PEX 8508 in this application.

Figure 3. Aggregation Adapter Card

The adapter card in Figure 3 is transparent with no local

processor present. Here four Gigabit Ethernet (GE) ports are

aggregated through the switch. Recent MAC/PHY devices for

GE all well as InfiniBand, Fibre Channel, etc., have native

PCI Express support for direct connections to the switch. The

non-blocking low latency design of PEX 8508 provides full

throughput with latency under 150ns.

Intelligent Adapter Card

The PEX 8508 supports the non-transparency feature. Figure 4

illustrates an intelligent adapter card used in servers and

storage hosts and is commonly used in TCP/IP Offload (TOE)

engines, iSCSI processing, RDMA, or encryption/decryption.

Figure 4. Intelligent Adapter

In this figure, the CPU on the adapter card is isolated from the

host CPU (not shown). The PEX 8508 non-transparent port

allows the two CPUs to be isolated but communicate with

each other through address translation that is integrated into

the PEX 8508. The upstream and downstream as well as the

non-transparent port of the PEX 8508 are fully configurable.

In this adapter, the CPU or other “intelligent” device with on-

chip processing capability—needs to be isolated from the rest

of the system to avoid memory mapping conflicts.

Office Automation Controller

A low port/lane PCI Express switch can be very useful in a

print engine or similar type system controller in embedded

applications. Such designs require low port/lane counts and

low cost, yet the system throughput can be very high for

graphics oriented data. Figure 5 shows that the PEX 8508 is

used to transfer data from a scanner and other input devices to

the print engine CPU and back to the marking engine. Many

endpoint devices will be incorporating native PCI Express

support to allow the use of all five ports of the PEX 8508.

Complete power management support will reduce system

power consumption. With a small 19mm x 19mm footprint,

the controller board space can be minimized.

Figure 5. Printer Controller Engine

ATCA and XMC Mezzanine Card Applications

The PEX 8508 supports aggregation or fan-in/out as well as

peer-to-peer switching. Figure 6 shows each I/O Mezzanine

card with a PEX 8508 which can aggregate data to the main

baseboard or allow peer-to-peer switching between I/O

endpoints. Non transparency can isolate each of the I/O

Mezzanine cards from each other.

Figure 6. XMC Mezzanine Card