Low Power with Granular SerDes Control

The PEX 8548 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 8548 supports a large number of port

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

using the PEX 8548 in a fan-out application, you may

configure the upstream port as a x16 and the

downstream as eight x4 ports; three x8 ports & two x4

ports; or various combinations, as long as you don’t run

out of lanes (48) or ports (9). For a dual-graphics

application, the device can be configured as three x16

ports.

PEX 8548

PEX 8548

PEX 8548

PEX 8548

x16

PEX 8548

PEX 8548

PEX 8548

PEX 8548

x16

PEX 8548

PEX 8548

PEX 8548

PEX 8548

x16

x16

x16

x8

x4 x4

x8

x8

PEX 8548

PEX 8548

PEX 8548

PEX 8548

x8

all x8

x8

x4 x4

x4

x8

x4

Figure 1. Common Port Configurations

Low Packet Latency

The PEX 8548 supports packet cut-thru with a

maximum packet latency of 110ns between symmetric

x16 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 8548 hot plug capability and

advanced error reporting features make it suitable for

High Availability (HA) applications. Three

downstream ports include a Standard Hot Plug

Controller. If the PEX 8548 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 8548 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 PEX 8548 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 8548 can be configured for a wide

variety of form factors and applications.

Host Centric Fan-out

The PEX 8548, with its symmetric or asymmetric lane

configuration capability, allows user-specific tuning to a

variety of host-centric applications.

CPU

CPU

CPU

CPU

PEX 8548

PEX 8548

PEX 8548

PEX 8548

Chip Set

Chip Set

Chip Set

Chip Set

End

Point

End

Point

End

Point

End

Point

x8 or x16

x4

Memory

Memory

Memory

Memory

x8

x8

Figure 2. Fan-in/out Usage