Flexible Port Configurations

The PEX 8604 flexible architecture supports a number of port

configurations as required by the target applications as shown

in figure 1 below.

Figure 1. Port Configurations

Hot-Plug for High Availability

Hot-Plug capability allows users to replace hardware modules

and perform maintenance without powering down the system.

The PEX 8604 Hot-Plug capability feature makes it suitable

for High Availability (HA) applications. If the PEX 8604 is

used in an application where one or more of its downstream

ports connect to PCI Express slots, each port’s Hot-Plug

Controller can be used to manage the Hot-Plug event of its

associated slot. Every port on the PEX 8604 is equipped with

a Hot-Plug control/status register to support Hot-Plug

capability through external logic via the I

Dual Cast

The PEX 8604 supports Dual Cast, a feature which allows for

the copying of data (e.g. packets) from one ingress port to two

egress ports allowing for higher performance in storage,

security, and mirroring applications.

Read Pacing

The Read Pacing feature allows users to throttle the amount of

read requests being made by downstream devices. In the case

where a downstream device requests several long reads back-

to-back, the Root Complex gets tied up in serving this

downstream port. If this port has a narrow link and is therefore

slow in receiving these read packets from the Root Complex,

then other downstream ports may become starved – thus,

impacting performance. The Read Pacing feature enhances

performances by allowing for the adequate servicing of all

downstream devices by intelligent handling of read requests.

SerDes Power and Signal Management

The PEX 8604 provides low power capability that is fully

compliant with the PCI Express power management

specification. In addition, the SerDes physical links can be

turned off when unused for even lower power. The PEX 8604

supports software control of the SerDes outputs to allow

optimization of power and signal strength in a system. The

PLX SerDes implementation supports four levels of power –

off, low, typical, and high. The SerDes block also supports

loop-back modes and advanced reporting of error

conditions, which enables efficient debug and management of

the entire system.

Port and Virtual Channel (VC) Arbitration

The PEX 8604 switch supports hardware fixed and Weighted

Round-Robin Ingress Port Arbitration. This allows fine tuning

of Quality of Service and efficient use of packet buffers for

better system performance. The PEX 8604 also supports WRR

VC arbitration scheme between the two virtual channels.

Applications

Suitable for fan-out, control plane applications, embedded

systems as well as intelligent I/O applications, PEX 8604

can be configured for a wide variety of form factors and

applications.

Fan-Out

The PEX 8604 switch, with its flexible configurations, allows

user specific tuning to a variety of host-centric as well as

peer-to-peer applications.

Figure 2. Fan-in/out Usage

Figure 2 shows a typical fan-out design, where the processor

provides a PCI Express link that needs to be fanned into a

larger number of smaller ports for a variety of I/O functions,

each with different bandwidth requirements.

In this example, the PEX 8604 would typically have a 1-lane

upstream port, and three downstream ports. The downstream

ports provide x1 PCI Express connectivity to the endpoints.

With its four ports, the PEX 8604 can provide fan-out

connectivity to up to three PCI Express devices. The figure

also shows how some of the ports can be bridged to provide

PCI slots through the use of the PEX 8112 PCIe bridging

devices.

Consumer Applications

With its small footprint, the PEX 8604 is ideal for consumer

applications. Figure 3 shows an example for a set top box.

The PEX8604 connects to legacy devices using a PEX85112