PLX Confidential

Low Power with Granular SerDes Control

The PEX 8525 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 width of each port can be individually configured

through auto-negotiation, hardware strapping, host

software configuration, I

optional EEPROM.

The PEX 8525 supports a large number of port

configurations (see Figure 1). For example, if you are

using the PEX 8525 in a fan-out application, you may

configure the upstream port as x8 and the downstream

ports as four x4 ports; two x8 ports; or other

combinations as long as you don’t run out of lanes (24)

or ports (5). In a peer-to-peer application, you can

configure all five ports as x4. In a port aggregation

application you can configure four x2 or x4 ports for

aggregation into one x8 port.

PEX 8525

PEX 8525

PEX 8525

PEX 8525

x8

x4 x4 x4

PEX 8525

PEX 8525

PEX 8525

PEX 8525

x8

PEX 8525

PEX 8525

PEX 8525

PEX 8525

x8

PEX 8525

PEX 8525

PEX 8525

PEX 8525

x4

x8

x8

x4

x4 x2 x2

x4

x4 x4 x4

x4

Figure 1. Common Port Configurations

Low Packet Latency

The PEX 8525 supports packet cut-thru with a max

packet latency of 115ns between symmetric x8 ingress

and egress ports. The low latency enables applications to

achieve high throughput and performance. In addition to

low latency, the device supports a packet payload size of

up to 1024 bytes, enabling the user to achieve even

higher throughput.

Hot Plug for High Availability

Hot plug capability allows users to replace hardware

modules and perform maintenance without powering

down the system. The PEX 8525 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 8525 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 8525 device support 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 PEX 8525 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.

Applications

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

patterns, the PEX 8525 can be configured for a wide

variety of form factors and applications.

Host Centric Fan-out

The PEX 8525, with its symmetric or asymmetric lane

configuration capability, allows user-specific tuning to a

variety of host-centric applications.

Figure 2 shows a

typical server-

based design where

the root complex

provides a PCI

Express link that

needs to be

expanded to a larger

number of smaller

ports for a variety

of I/O functions. In

this example, the

PEX 8525 would

Figure 2. Fan-in/out Usage

typically have an 8-lane upstream port, and as many as

CPU

CPU

Memory

Memory

Chip Set

Chip Set

End

Point

End

Point

x8

x4

PEX 8525

PEX 8525

x4

x4

x4

CPU

CPU

CPU

CPU

Memory

Memory

Memory

Memory

Chip Set

Chip Set

Chip Set

Chip Set

End

Point

End

Point

End

Point

End

Point

x8

x4

PEX 8525

PEX 8525

PEX 8525

PEX 8525

x4

x4

x4