Flexible Port Configurations
The PEX 8604 flexible architecture supports a number of port
configurations as required by the target applications as shown
in figure 1 below.
off, low, typical, and high. The SerDes block also supports
loop-back modes
and
advanced reporting of error
conditions,
which enables efficient debug and management of
the entire system.
Port and Virtual Channel (VC) Arbitration
The PEX 8604 switch supports hardware fixed and Weighted
Round-Robin Ingress Port Arbitration. This allows fine tuning
of Quality of Service and efficient use of packet buffers for
better system performance. The PEX 8604 also supports WRR
VC arbitration scheme between the two virtual channels.
Applications
Suitable for
fan-out, control plane applications, embedded
systems
as well as
intelligent I/O applications,
PEX 8604
can be configured for a wide variety of form factors and
applications.
Figure 1. Port Configurations
Fan-Out
The PEX 8604 switch, with its flexible configurations, allows
user specific tuning to a variety of
host-centric as well as
peer-to-peer applications.
Hot-Plug for High Availability
Hot-Plug capability allows users to replace hardware modules
and perform maintenance without powering down the system.
The PEX 8604 Hot-Plug capability feature makes it suitable
for
High Availability (HA) applications.
If the PEX 8604 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 8604 is equipped with
a Hot-Plug control/status register to support Hot-Plug
capability through external logic via the I
2
C interface
.
Dual Cast
The PEX 8604 supports Dual Cast, a feature which allows for
the copying of data (e.g. packets) from one ingress port to two
egress ports allowing for higher performance in storage,
security, and mirroring applications.
Read Pacing
The Read Pacing feature allows users to throttle the amount of
read requests being made by downstream devices. In the case
where a downstream device requests several long reads back-
to-back, the Root Complex gets tied up in serving this
downstream port. If this port has a narrow link and is therefore
slow in receiving these read packets from the Root Complex,
then other downstream ports may become starved – thus,
impacting performance. The Read Pacing feature enhances
performances by allowing for the adequate servicing of all
downstream devices by intelligent handling of read requests.
Figure 2. Fan-in/out Usage
Figure 2 shows a typical
fan-out
design, where the processor
provides a PCI Express link that needs to be fanned into a
larger number of smaller ports for a variety of I/O functions,
each with different bandwidth requirements.
In this example, the PEX 8604 would typically have a 1-lane
upstream port, and three downstream ports. The downstream
ports provide x1 PCI Express connectivity to the endpoints.
With its four ports, the PEX 8604 can provide fan-out
connectivity to up to three PCI Express devices. The figure
also shows how some of the ports can be bridged to provide
PCI slots
through the use of the
PEX 8112 PCIe
bridging
devices.
SerDes Power and Signal Management
The PEX 8604 provides low power capability that is fully
compliant with the PCI Express power management
specification. In addition, the SerDes physical links can be
turned off when unused for even lower power. The PEX 8604
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 –
Consumer Applications
With its small footprint, the PEX 8604 is ideal for consumer
applications. Figure 3 shows an example for a set top box.
The PEX8604 connects to legacy devices using a PEX85112
PLX [ PLX TECHNOLOGY ]
