Flexible Port Configuration
The lane width for each port can be individually configured
through auto-negotiation, hardware strapping, upstream
software configuration, or through an optional EEPROM.
The PEX 8508 supports a large number of port configurations.
For example, if you are using the PEX 8508 in a fan-out
application, you may configure the upstream port as x4 and
the downstream ports as four x1 ports or two x2. In a peer-to-
peer switch aggregation application you can configure four x2
ports. Figure 1 show most common port configurations.
also supports
loop-back
modes and
advanced reporting of
error conditions,
which enables efficient debug and
management of the entire system.
Flexible Virtual Channel Arbitration
The PEX 8508 switch supports fixed priority and Round
Robin arbitration schemes for up to two virtual channels. This
allows fine tuning of Quality of Service, efficient use of
packet buffers and the system bandwidth.
Applications
Suitable for host-centric as well as Intelligent I/O applications
the PEX 8508 can be configured for a wide variety of form
factors and applications.
Processor Isolation for Redundancy
The PEX 8508 switch, with its low latency, Hot-Plug, and
NTB capability, allows users to isolate processors in
multi-
host or failover applications.
Figure 1. Common Port Configurations
Hot-Plug for High Availability
Hot plug capability allows users to replace hardware modules
and perform maintenance without powering down the system.
The PEX 8508 hot-plug capability and
Advanced Error
Reporting
features makes it suitable for
High Availability
(HA)
applications. Each port includes a Standard
Hot-Plug
Controller.
If the PEX 8508 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. Furthermore, its
upstream port is a
hot-plug client,
allowing it to be used on
hot-pluggable
adapter cards, backplanes and fabric
modules.
Figure 2. Processor Isolation
Figure 2 shows two server boards. The PCI Express switch is
used to prevent the backup host from enumerating and
configuring portions of the primary host system. In addition,
non transparent ports provide doorbell and mailbox registers
for inter-processor communications. The backup processor
will monitor heartbeat messages from the primary system and
upon failure take over as the primary host.
PEX 8508 has very
low latency,
under
150ns,
to assist in a
rapid failover to the backup system. Here only one PEX 8508
switch is required with the one non transparent port but to
maintain identical board layouts, each board shown has a
PEX 8508 switch. This application can be generalized to
where each
compute
or
storage
or
I/O board
would include a
PEX 8508 to isolate each processor domain.
Fully Compliant Power Management
For applications that require power management, the
PEX 8508 devices support both link (L0, L0s, L1, L2/L3
Ready, L2 and L3) and device (D0 and D3hot) power
management states, in compliance with the PCI Express power
management specification. Vaux, Wake# and Beacon support
the wakeup protocol from the D3cold state.
SerDes Power and Signal Management
The PEX 8508 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
Adapter Card Aggregation
The number and variety of PCI Express native-mode devices
is growing quickly. As these devices become mainstream it
will be necessary to create multifunction and multi-port
adapter cards with PCI Express capability.
PLX [ PLX TECHNOLOGY ]
