Flexible Port Configurations

The PEX 8608 supports the port configurations as shown in

figure 1 below. The figure shows an 8-port configuration, a 5-

port configuration as well as a 2-port configuration.

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 8608 Hot-Plug capability feature makes it suitable

for High Availability (HA) applications. If the PEX 8608 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 8608 is equipped with

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

capability through external logic via the I

Dual Cast

The PEX 8608 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 8608 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 8608

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 8608 switch supports hardware fixed and Weighted

Round-Robin (WRR) Ingress Port Arbitration. This allows

fine tuning of Quality of Service and efficient use of packet

buffers for better system performance. The PEX 8608 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 and host isolation

applications, PEX 8608 can be configured for a wide variety

of form factors and applications.

Fan-Out

The PEX 8608 switch, with its high port count and flexible

configurations, allows user specific tuning to a variety of host-

centric as well as peer-to-peer applications.

Contro

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 8608 would typically have a 1-lane

upstream port, and as many as 7 downstream ports. The

downstream ports provide x1 PCI Express connectivity to the

endpoints. With its eight ports, the PEX 8608 can provide fan-

out connectivity to up to seven PCI Express devices. The

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

provide PCI slots or Generic devices through the use of the

PEX 8311 and PEX 8112 PCIe bridging devices.

Processor

Contro

Processor

Memory

Memory

PEX 8608

PEX 8608

PEX 8608

PEX 8608

PCI

PCI

PCI

PCI

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

PCIe

FPGA

FPGA

FPGA

FPGA

PEX 8112

PEX 8112

PEX 8112

PEX 8112

DSP

DSP

DSP

DSP

PEX 8311

PEX 8311

PEX 8311

PEX 8311