Low Power with Granular SerDes Control
The PEX 8525 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.
Flexible Port Width Configuration
The width of each port can be individually configured
through auto-negotiation, hardware strapping, host
software configuration, I
2
C interface, or through an
optional EEPROM.
The PEX 8525 supports a large number of port
configurations (see Figure 1). For example, if you are
using the PEX 8525 in a fan-out application, you may
configure the upstream port as x8 and the downstream
ports as four x4 ports; two x8 ports; or other
combinations as long as you don’t run out of lanes (24)
or ports (5). In a peer-to-peer application, you can
configure all five ports as x4. In a port aggregation
application you can configure four x2 or x4 ports for
aggregation into one x8 port.
x8
x8
Advanced Error Reporting
features makes it suitable
for
High Availability (HA) applications.
Three
downstream ports include a Standard Hot Plug
Controller. If the PEX 8525 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.
Fully Compliant Power Management
For applications that require power management, the
PEX 8525 device support both link (L0, L0s, L1, L2/L3
Ready, and L3) and device (D0 and D3hot) power
management states, in compliance with the PCI Express
power management specification.
SerDes Power and Signal Management
The PEX 8525 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.
PEX 8525
PEX 8525
Applications
x4 x4 x4 x4
x8
x8
x8
x4
Suitable for
host-centric
as well as
peer-to-peer traffic
patterns,
the PEX 8525 can be configured for a wide
variety of form factors and applications.
Host Centric Fan-out
The PEX 8525, with its symmetric or asymmetric lane
configuration capability, allows user-specific tuning to a
variety of host-centric applications.
Figure 2 shows a
CPU
typical
server-
based
design where
Memory
Chip Set
the root complex
provides a PCI
x8
Express link that
needs to be
PEX 8525
expanded to a larger
x4
number of smaller
x4
x4
ports for a variety
End
of I/O functions. In
x4
Point
this example, the
PEX 8525 would
Figure 2. Fan-in/out Usage
typically have an 8-lane upstream port, and as many as
PEX 8525
PEX 8525
x4 x4 x2 x2
x4 x4 x4 x4
Figure 1. Common Port Configurations
Low Packet Latency
The PEX 8525 supports packet
cut-thru
with a max
packet latency of 115ns between symmetric x8 ingress
and egress ports. The low latency enables applications to
achieve high throughput and performance. In addition to
low latency, the device supports a packet payload size of
up to 1024 bytes, enabling the user to achieve even
higher throughput.
Hot Plug for High Availability
Hot plug capability allows users to replace hardware
modules and perform maintenance without powering
down the system. The PEX 8525 hot plug capability and
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