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 8516 supports a large number of port configurations.

For example, if you are using the PEX 8516 in a fan-out

application, you may configure the upstream port as x8 and

the downstream ports as three x2 ports; two x2 & one x4

ports; three x1 ports; or other combinations, as long as you

don’t run out of lanes (16) or ports (4). In a port aggregation

application you can configure three x2 or x1 ports for

aggregation into one x8 or x4 port. 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 8516 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 8516 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

8516 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 8516 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 8516 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 intelligent I/O

applications ExpressLane PEX 8516 can be configured for a

wide variety of form factors and applications.

Host-Centric Fan-out

The ExpressLane PEX 8516 switch, with its symmetric or

asymmetric lane configuration capability, 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 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 8516 would typically have an 8-lane

upstream port, and as many as 3 downstream ports. 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.

Adapter Card Aggregation

The number and variety of PCI Express native-mode devices

is growing quickly. As these devices become mainstream, it

will be necessary to create multifunction and multi-port

adapter cards with PCI Express capability.