PEX8724 datasheet(4/5 Pages) PLX

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PEX 8724, PCI Express Gen 3 Switch, 24 Lanes, 6 Ports

Error Injection & SerDes Loopback

Using the PEX 8724’s Error Injection feature, users can

inject malformed packets and/or fatal errors into their

system and evaluate a system’s ability to detect and

recover from such errors. The PEX 8724 also supports

Internal Tx, External Tx, Recovered Clock, and Recovered

Data Loopback modes.

Applications

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

patterns, the PEX 8724 can be configured for a wide

variety of form factors and applications.

Host Centric Fan-out

The PEX 8724, with its symmetric or asymmetric lane

configuration capability, allows user-specific tuning to a

variety of host-centric applications. Figure 6 shows a

server design where, in a quad or multi processor system,

users can assign endpoints/slots to CPU cores to distribute

the system load. The packets directed to different CPU

cores will go to different (user assigned) PEX 8724

upstream ports, allowing better queuing and load balancing

capability for higher performance. Conversely, the PEX

8724 can also be used in single-host mode to simply fan-

out to endpoints.

Memory

CPU

Memory

CPU

x4s

x2s

x1s

SATA

Endpoint

PCIe Gen1, Gen2, or Gen3 slots

PEX 8724

PCI

PCH

Figure 6. Host Centric Dual Upstream

Host Failover

The PEX 8724 can also be utilized in applications where

host failover is required. In the below application (Figure

7), two hosts may be active simultaneously and controlling

their own domains while exchange status information

through doorbell registers or I

2C interface. The devices can

be programmed to trigger fail-over if the heartbeat

information is not provided. In the event of a failure, the

surviving device will reset the endpoints connected to the

failing CPU and enumerate them in its own domain

without impacting the operation of endpoints already in its

domain.

CPU

PEX 8724

CPU

PEX 8724

x4s

Figure 7. Host Fail-Over

Fail-Over in Storage Systems with Multicast

The PEX 8724’s Multicast feature can be used to

simultaneously send redundant packets to a backup system

(Figure 8). In the example below, using Multicast (yellow

lines), the CPU sends data to its endpoints as well as to a

backup system (via an NT port) in one transaction as

opposed to having to send multiple transactions to each

endpoint. By offloading the task of backing up data onto

the secondary system, processor and system performance

is enhanced.

Memory

CPU

Memory

CPU

PEX 8724

8 Disk Chassis

PEX 7616

8 Disk Chassis

Control

PEX 8716

Backup

System

PEX

8724

PEX

8724

Figure 8. N+1 Failover

Page 4 of 5

10/7/2010, Version 1.0

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