PEX 8717, PCI Express Gen 3 Switch, 16 Lanes, 10 Ports

© PLX Technology, www.plxtech.com

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8/1/2011, Version 1.0

The PEX 8717 can also be configured in Multi-Host mode

where users can choose up to two 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 8717 in Multi-Host mode where each ellipse

represents a virtual switch inside the device.

The PEX 8717 also provides

several ways to configure its

registers. The device can be

configured through strapping

pins, I

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

In Single-Host mode, the PEX 8717 supports 2 Non-

Transparent (NT) Ports, 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 8717 can be configured with up

to two upstream host ports, each with its own dedicated

downstream ports. The device can be configured for 1+1

redundancy. The PEX 8717 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.

Hot Plug for High Availability

Hot plug capability allows users to replace hardware

modules and perform maintenance without powering down

the system. The PEX 8717 hot plug capability feature

makes it suitable for High Availability (HA)

applications. Three downstream ports include a Standard

Hot Plug Controller. If the PEX 8717 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 8717 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 8717 provides low power capability that is fully

compliant with the PCIe power management specification

and supports software control of the SerDes outputs to

allow optimization of power and signal strength in a

system. Furthermore, the SerDes block supports loop-back

modes and advanced reporting of error conditions,

which enables efficient management of the entire system.

Interoperability

The PEX 8717 is designed to be fully compliant with the

PCI Express Base Specification r3.0, and is backwards

compatible to PCI Express Base Specification r2.0, r1.1,