Flexible Port Width Configuration

The lane width for each port can be individually configured

through auto-negotiation, hardware strapping, upstream

software configuration, or through an optional EEPROM.

The PEX 8524 supports a large number of port configurations.

For example, if you are using the PEX 8524 in a fan-out

application, you may configure the upstream port as x8 and

the downstream ports as four x4 ports; two x8 ports for dual-

graphics fan-out; or other combinations, as long as you don’t

run out of lanes (24) or ports (6). In a peer-to-peer application

you can configure all six ports as x4. Figure 1 shows the most

common port configurations.

Figure 1. Common 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 8524 hot plug capability and Advanced Error

Reporting features makes it suitable for High Availability

(HA) applications. Each downstream port includes a Standard

Hot Plug Controller. If the PEX 8524 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. Furthermore,

its upstream port is a hot-plug client, allowing it to be used

on hot-pluggable adapter cards, backplanes, and fabric

modules.

Fully Compliant Power Management

For applications that require power management, the PEX

8524 device supports both link (L0, L0s, L1, L2/L3 Ready,

and L3) and device (D0 and D3hot) power management states,

in compliance with the PCI Express power management

specification.

SerDes Power and Signal Management

The ExpressLane PEX 8524 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.

Flexible Virtual Channel Arbitration

The ExpressLane PEX 8524 switches support hardware fixed

and Round Robin arbitration schemes for two virtual

channels on each port. This allows for the fine tuning of

Quality of Service for efficient use of packet buffers and

system bandwidth.

Applications

Suitable for host-centric as well as peer-to-peer traffic

patterns, the PEX 8524 can be configured for a wide variety

of form factors and applications.

Host-Centric Fan-out

The PEX 8524, with its symmetric or asymmetric lane

configuration capability, allows user specific tuning to a

variety of host-centric applications.

Figure 2. Fan-in/out Usage

Figure 2 shows a typical server-based design, where the root

complex 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 8524 would typically have an 8-lane

upstream port, and as many as 5 downstream ports (4 shown

here). The downstream ports can be of differing widths if

required. The figure also shows how some of the ports can be

bridged to provide PCI or PCI-X slots through the use of the

ExpressLane PEX 8114 and PEX 8111 PCIe bridging

devices.