PEX 8680, PCI Express Gen 2 Switch, 80 Lanes, 20 Ports

© PLX Technology, www.plxtech.com

Page 2 of 2

5/14/2009, Version 1.1

The PEX 8680 can also be configured in Multi-Host

mode where users can choose up to six ports as

host/upstream ports and assign a desired number of

downstream ports to each host. In Multi-Host mode, a

virtual switch is created for each host port and its

associated downstream ports inside the device. The

traffic between the ports of a virtual switch is completely

isolated from the traffic in other virtual switches. Figure

2 illustrates some configurations of the PEX 8680 in

Multi-Host mode where each ellipse represents a virtual

switch inside the device.

Figure 2. Common Multi-Host Configurations

PEX 8680

PEX 8680

PEX 8680

PEX 8680

x8

2 x8, 4x4

2 x8, 4 x4

x8

PEX 8680

PEX 8680

PEX 8680

PEX 8680

x8

4 x4

4 x4

x8

x8

4 x4

PEX 8680

PEX 8680

PEX 8680

PEX 8680

16 x4s

4 x4s

PEX 8680

PEX 8680

PEX 8680

PEX 8680

12 x4s

6 x4s

The PEX 8680

also provides

several ways to

configure its

registers. The

device can be

configured

through

strapping pins,

I

host software,

or

an optional

serial

EEPROM.

This allows

for easy debug during the development phase,

performance monitoring during the operation phase, and

driver or software upgrade.

Dual-Host & Failover Support

CPU

CPU

Primary Host

Primary Host

Root

Complex

Root

Complex

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

PEX 8680

PEX 8680

NT

CPU

CPU

Secondary Host

Secondary Host

Non-Transparent

Port

Figure 3. Non-Transparent Port

CPU

CPU

Primary Host

Primary Host

CPU

CPU

Primary Host

Primary Host

Root

Complex

Root

Complex

Root

Complex

Root

Complex

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

PEX 8680

PEX 8680

NT

CPU

CPU

Secondary Host

Secondary Host

CPU

CPU

Secondary Host

Secondary Host

Non-Transparent

Port

Figure 3. Non-Transparent Port

In Single-Host mode, the PEX 8680 supports a Non-

Transparent (NT) Port, which enables the

implementation of dual-host systems for redundancy

and host failover capability.

The NT port allows systems

to isolate host memory

domains by presenting the

processor subsystem as an

endpoint rather than

another memory system.

Base

address registers are used

to translate addresses;

doorbell registers are

used to send

interrupts between the

address domains; and scratchpad registers (accessible by

both CPUs) allow inter-processor communication (see

Figure 3).

Multi-Host & Failover Support

In Multi-Host mode, PEX 8680 can be configured with

up to six upstream host ports, each with its own

dedicated downstream ports. The device can be

configured for 1+1 redundancy or N+1 redundancy. The

PEX 8680 allows the hosts to communicate their status

to each other via special door-bell registers. In failover

mode, if a host fails, the host designated for failover will

disable the upstream port attached to the failing host and

program the downstream ports of that host to its own

domain. Figure 4a shows a two host system in Multi-

Host mode with two virtual switches inside the device

and Figure 4b shows Host 1 disabled after failure and

Host 2 having taken over all of Host 1’s end-points.

PEX 8680

PEX 8680

PEX 8680

PEX 8680

Figure 4a. Multi-Host

Host 1

Host 1

Host 1

Host 1

Host 2

Host 2

Host 2

Host 2

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

Figure 4b. Multi-Host Fail-Over

Host 1

Host 1

Host 1

Host 1

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

End

Point

Host 2

Host 2

Host 2

Host 2

Hot Plug for High Availability

Hot plug capability allows users to replace hardware

modules and perform maintenance without powering

down the system. The PEX 8680 hot plug capability

feature makes it suitable for High Availability (HA)

applications. Four downstream ports include a Standard

Hot Plug Controller. If the PEX 8680 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. Every port on the PEX 8680 is

equipped with a hot-plug control/status register to

support hot-plug capability through external logic via the

I

SerDes Power and Signal Management

The PEX 8680 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 management of the entire system.

Interoperability

The PEX 8680 is designed to be fully compliant with the

PCI Express Base Specification r2.0, and is backwards

compatible to PCI Express Base Specification r1.1 and