Flexible Port Configurations
The PEX 8615 supports a large number of port configurations
as shown in figure 1 below. Please refer to the PEX 8615
datasheet for more port configuration options.
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 8615 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 8615 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 8615
can be configured for a wide variety of form factors and
applications.
Figure 1. PEX8615 Port Configurations
Fan-Out
The PEX 8615 switch, with its high port count and 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 8615 Hot-Plug capability feature makes it suitable
for
High Availability (HA) applications.
If the PEX 8615 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 8615 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 8615 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 8615 would typically have a 1-lane
upstream port, and as many as 11 downstream ports. The
downstream ports provide x1 PCI Express connectivity to the
endpoints. With its twelve ports, the PEX 8615 can provide
fan-out connectivity to up to eleven PCI Express devices. The
figure also shows how some of the ports can be bridged to
provide
PCI slots or Generic devices
through the use of the
PEX 8311 and PEX 8112 PCIe
bridging devices.
SerDes Power and Signal Management
The PEX 8615 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 8615
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 –
Control Plane Application
The PEX 8615 is ideal for control planes in routers and other
communications sub-systems to meet increased packet
processing needs without compromising latency. Figure 3
PLX [ PLX TECHNOLOGY ]
