management states, in compliance with the PCI Express power
management specification.
Low Power with Granular SerDes Control
The PEX 8518 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.
SerDes Power and Signal Management
The ExpressLane PEX 8518 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 debug
and management of the entire system.
Flexible Port Width 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 8518 supports a large number of port configurations.
For example, if you are using the PEX 8518 in a fan-out
application, you may configure the upstream port as x8 and
the downstream ports as four x2 ports; two x2 & one x4 ports;
three x1 ports; or other combinations, as long as you don’t run
out of lanes (16) or ports (5). In a port aggregation application
you can configure three x2 or x1 ports for aggregation into one
x8 or x4 port. Figure 1 shows the most common port
configurations.
Flexible Virtual Channel Arbitration
The ExpressLane PEX 8518 switch supports hardware fixed
and Round Robin arbitration schemes for two virtual
channels on each port. This allows for the fine tuning of
Quality of Service for efficient use of packet buffers and
system bandwidth.
Applications
Suitable for host-centric as well as intelligent I/O
applications ExpressLane PEX 8518 can be configured for a
wide variety of form factors and applications.
Host-Centric Fan-out
The ExpressLane PEX 8518 switch, with its symmetric or
asymmetric lane configuration capability, allows user specific
tuning to a variety of host-centric as well as peer-to-peer
applications.
Figure 1. Common Port Configurations
Hot-Plug for High Availability
Figure 2. Fan-in/out Usage
Hot plug capability allows users to replace hardware modules
and perform maintenance without powering down the system.
The PEX 8518 hot-plug capability and Advanced Error
Reporting features makes it suitable for High Availability
(HA) applications. Each downstream port includes a Standard
Hot-Plug Controller. If the PEX 8518 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 shows a typical server-based design, where the root
complex 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 8518 would typically have an 8-lane
upstream port, and as many as three downstream ports. The
downstream ports can be of differing widths if required. The
figure also shows how some of the ports can be bridged to
provide PCI or PCI-X slots through the use of the
ExpressLane PEX 8114 and PEX 8111 PCIe bridging
devices.
Fully Compliant Power Management
Adapter Card Aggregation
For applications that require power management, the
PEX 8518 device supports both link (L0, L0s, L1, L2/L3
Ready, L2 and L3) and device (D0 and D3hot) power
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
PLX [ PLX TECHNOLOGY ]
