Low Power with Granular SerDes Control

The PEX 8512 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.

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 8512 supports two port configurations as shown in

Figure 1. Depending on the application, the PEX 8512 can be

configured to have Three ports each with x4 link widths or

Five ports one port with x4 link width and four ports with x2

link widths.

PEX 8512

PEX 8512

PEX 8512

PEX 8512

x4

x4

x4

PEX 8512

PEX 8512

x4

x2

x2

x2

x2

PEX 8512

PEX 8512

x4

x4

x2 x2

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 8512 hot-plug capability and Advanced Error

Reporting features makes it suitable for High Availability

(HA) applications. Three downstream ports include a

Standard Hot-Plug Controller. If the PEX 8512 is used in an

application where one or more of its downstream ports

connect to

PCI Express slots, the 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 8512 device supports both link (L0, L0s, L1, L2/L3

Ready, L2 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 8512 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 8512 switch supports 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 8512 can be configured for a

wide variety of form factors and applications.

Host-Centric Fan-out

The ExpressLane PEX 8512 switch, with its symmetric 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 ports for a variety of I/O functions,

each with different bandwidth requirements.

In this example, the PEX 8512 would typically have a 4-lane

upstream port, and two downstream ports. The downstream

ports are configured with x4 link widths.

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. The PEX 8512 can

be used to create an adapter or mezzanine card that aggregates

the PCI Express devices into a single port that can be plugged