PEX 8696, PCI Express Gen 2 Switch, 96 Lanes, 24 Ports
The PEX 8696 can also be configured in Multi-Host
mode where users can choose up to eight 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 8696 in
Multi-Host mode where each ellipse represents a virtual
switch inside the device.
x16
x16
x8 x8 x8
PEX 8696 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.
Host
1
Host
2
Host
1
Host
2
PEX 8696
PEX 8696
The PEX 8696 also
provides several ways to
PEX 8696
PEX 8696
configure its registers. The
2 x8, 4 x4 2 x8, 4x4
6 x4 6 x4 6 x4
device can be configured
4 x4s
8 x4s
through strapping pins,
2
I C interface,
host
software, or an optional
PEX 8696
PEX 8696
serial EEPROM. This
allows for easy debug
20 x4s
2 x8, 12 x4s
Figure 2. Common Multi-Host Configurations
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 8696 supports a
Non-
Transparent (NT) Port,
which enables the
implementation of
dual-host systems
for redundancy
and host failover capability.
Primary Host
Secondary Host
Primary Host
Secondary Host
CPU
CPU
The NT port allows systems
to isolate host memory
domains by presenting the
Root
Complex
processor subsystem as an
endpoint rather than another
NT
memory system. Base
PEX 8696
Non-Transparent
address registers are used
Port
to translate addresses;
End
End
End
doorbell registers are
used
Point
Point
Point
to send interrupts
Figure 3. Non-Transparent Port
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 8696 can be configured with
up to eight upstream host ports, each with its own
dedicated downstream ports. The device can be
configured for 1+1 redundancy or N+1 redundancy. The
End
Point
End
Point
End
Point
End
Point
End
Point
End
Point
End
Point
End
Point
Figure 4a. Multi-Host
Figure 4b. Multi-Host Fail-Over
Hot Plug for High Availability
Hot plug capability allows users to replace hardware
modules and perform maintenance without powering
down the system. The PEX 8696 hot plug capability
feature makes it suitable for
High Availability (HA)
applications.
Four downstream ports include a Standard
Hot Plug Controller. If the PEX 8696 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 8696 is
equipped with a hot-plug control/status register to
support hot-plug capability through external logic via the
I
2
C interface.
SerDes Power and Signal Management
The PEX 8696 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 8696 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
8696 is tested for Microsoft Vista compliance. All PLX
switches undergo thorough interoperability testing in
PLX’s
Interoperability Lab
and
compliance testing at
the PCI-SIG plug-fest.
5/14/2009, Version 1.1
© PLX Technology, www.plxtech.com
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