PEX 8716, PCI Express Gen 3 Switch, 16 Lanes, 4 Ports

© PLX Technology, www.plxtech.com

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10/7/2010, Version 1.0

Figure 2. Multi-Host

Port Configuration

PEX

8712

x4

x4

x4

The PEX 8716 can also be configured in Multi-Host mode.

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. With the PEX 8712 in

Multi-Host mode, users can choose

two ports as host/upstream ports and

assign the downstream ports to the

desired host. In this scenario, one of

the hosts will serve as a failover port

which will not have a downstream port of its own. If the

primary host were to fail, the secondary host would then

take over this downstream port (see Figure 2).

End

Point

CPU

Primary Host

Root

Complex

PEX 8716

NT

CPU

Secondary Host

Non-Transparent

Port

Figure 3. Non-Transparent Port

End

Point

The PEX 8716 also provides several ways to configure its

registers. The device can be configured through strapping

pins, I

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 8716 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 8716 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 or N+1 redundancy. The PEX 8716 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 8716

PEX 8716

Figure 4a. Multi-Host

Host 1

Host 2

End

Point

Figure 4b. Multi-Host Fail-Over

Host 1

Host 2

End

Point

End

Point

End

Point

Hot Plug for High Availability

Hot plug capability allows users to replace hardware

modules and perform maintenance without powering down

the system. The PEX 8716 hot plug capability feature

makes it suitable for High Availability (HA)

applications. Three downstream ports include a Standard

Hot Plug Controller. If the PEX 8716 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 8716 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 8716 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 8716 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

r1.0a. Additionally, it supports auto-negotiation, lane

reversal, and polarity reversal. Furthermore, the PEX

8716 is tested for Microsoft Vista compliance. All PLX