Version 1.2 2009
Features
PEX 8608 General Features
o 8-lane PCI Express switch
- Integrated 5.0 GT/s SerDes
o Up to 8 configurable ports
o 15 x 15mm2, 196-ball PBGA
o Typical Power: 1.39 Watts
PEX 8608 Key Features
o Standards Compliant
- PCI Express Base Specification r2.0
(Backwards compatible with PCIe
r1.0a/1.1)
- PCI Power Management Spec r1.2
- Microsoft Vista Compliant
- Supports Access Control Services
- Dynamic link-width control
- Dynamic SerDes Speed Control
o High Performance
- Non-blocking internal architecture
- Full line rate on all ports
- Cut-Thru latency: 130ns
- 2KB max payload size
- Read Pacing
(intelligent bandwidth allocation)
- Dual Cast
o Dual-Host & Fail-Over Support
- Configurable Non-Transparent port
- Moveable upstream port
- Crosslink port capability
o Flexible Configuration
- 8 flexible & configurable ports
(x1 or x4)
- Configurable with strapping pins,
EEPROM, I2C, or Host software
- Lane and polarity reversal
o PCI Express Power Management
- Link power management states: L0, L0s,
L1, L2/L3 Ready, and L3
- Device states: D0 and D3hot
o Spread Spectrum Clock Isolation
- Dual clock domain
o Quality of Service (QoS)
- Two Virtual Channels (VC) per port
- Eight Traffic Classes per port
- Weighted Round-Robin Port & VC
Arbitration
o Reliability, Availability, Serviceability
- All ports Hot-Plug capable thru I2C
(Hot-Plug Controller on every port)
- ECRC & Poison bit support
- Data path protection
- Memory (RAM) error correction
- Advanced Error Reporting support
- Port Status bits and GPIO available
- Per port error diagnostics
- Performance monitoring
(per port payload & header counters)
- JTAG AC/DC boundary scan
- Fatal Error (FATAL_ERR#) output signal
- INTA# output signal
PEX 8608
PCIe Gen2, 5.0 GT/s 8-lane 8-port PCI Express® Switch
The ExpressLane™ PEX 8608 device offers PCI Express switching capability
enabling users to add scalable high bandwidth non-blocking interconnection to a
wide variety of applications including communications platforms, control plane
applications and embedded systems. The PEX 8608 is well suited for fan-out,
aggregation, peer-to-peer, and intelligent I/O module applications.
Low Packet Latency & High Performance
The PEX 8608 architecture supports packet cut-thru with a maximum latency of
130ns in x4 to x1 configuration. This, combined with large packet memory and
non-blocking internal switch architecture, provides full line rate on all ports for lowlatency applications such as communications and embedded. The low latency
enables applications to achieve high throughput and performance. In addition to low
latency, the device supports a max payload size of 2048 bytes, enabling the user to
achieve even higher throughout.
Data Integrity
The PEX 8608 provides end-to-end CRC protection (ECRC) and Poison bit support
to enable designs that require guaranteed error-free packets. PLX also supports
data path parity and memory (RAM) error correction as packets pass through the
switch.
Dual-Host and Fail-Over Support
The PEX 8608 supports full non-transparent bridging (NTB) functionality to allow
implementation of multi-host systems and intelligent I/O modules in applications
which require redundancy support such as communications, storage, and servers.
Non-transparent bridges allow systems to isolate host memory domains by
presenting the processor subsystem as an endpoint rather than another memory
system. Base address registers are used to translate addresses; doorbell registers are
used to send interrupts between the address domains; and scratchpad registers are
accessible from both address domains to allow inter-processor communication.
Interoperability
The PEX 8608 is designed to be fully compliant with the PCI Express Base
Specification r2.0 and is backwards compatible to PCI Express Base Specification
r1.1 and r1.0a. Additionally each port supports auto-negotiation, lane reversal and
polarity reversal. Furthermore, the PEX 8608 is designed for Microsoft Vista
compliance. All PLX switches undergo thorough interoperability testing in PLX’s
Interoperability Lab and compliance testing at the PCI-SIG plug-fest to ensure
compatibility with PCI Express devices in the market.
Device Operation Configuration Flexibility
The PEX 8608 provides several ways to configure its operations. The device can be
configured through strapping pins, I2C interface, CPU configuration cycles and/or an
optional serial EEPROM. This allows for easy debug during the development phase
and functional monitoring during the operation phase.
Flexible Port Configurations
The PEX 8608 supports the port configurations as shown in
figure 1 below. The figure shows an 8-port configuration, a 5port configuration as well as a 2-port configuration.
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.
Port and Virtual Channel (VC) Arbitration
The PEX 8608 switch supports hardware fixed and Weighted
Round-Robin (WRR) Ingress Port Arbitration. This allows
fine tuning of Quality of Service and efficient use of packet
buffers for better system performance. The PEX 8608 also
supports WRR VC arbitration scheme between the two virtual
channels.
Applications
Figure 1. 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 8608 Hot-Plug capability feature makes it suitable
for High Availability (HA) applications. If the PEX 8608 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 8608 is equipped with
a Hot-Plug control/status register to support Hot-Plug
capability through external logic via the I2C interface.
Dual Cast
The PEX 8608 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.
Suitable for fan-out, control plane applications, embedded
systems as well as intelligent I/O and host isolation
applications, PEX 8608 can be configured for a wide variety
of form factors and applications.
Fan-Out
The PEX 8608 switch, with its high port count and flexible
configurations, allows user specific tuning to a variety of hostcentric as well as peer-to-peer applications.
Control
Processor
PCIe
PCIe
Memory
PEX 8311
DSP
PEX 8112
PCI
PEX 8608
FPGA
PCIe
PCIe
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 backto-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.
SerDes Power and Signal Management
The PEX 8608 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 8608
supports software control of the SerDes outputs to allow
optimization of power and signal strength in a system. The
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 8608 would typically have a 1-lane
upstream port, and as many as 7 downstream ports. The
downstream ports provide x1 PCI Express connectivity to the
endpoints. With its eight ports, the PEX 8608 can provide fanout connectivity to up to seven 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.
Control Plane Application
Intelligent Adapter Card
The PEX 8608 is ideal for control planes in routers and other
communications sub-systems to meet increased packet
processing needs without compromising latency. Figure 3
shows a controller card with a PEX 8608 connecting the
Control Processor to as many as seven line cards each via an
x1 connection. This usage model provides connectivity to
multiple line cards giving the processor control over a large
number of line cards in communication platforms.
The PEX 8608 supports the non-transparency feature.
Figure 6 illustrates a host system using an intelligent adapter
card.
Figure 6. Intelligent Adapter Usage
Figure 3. Control Plane Application
Control Planes for Large Systems
Two PEX 8608 devices can be used in applications where
there is need for more than 7 line cards and the processor has 2
PCIe ports. An example of a control plane application with
more than 7 line cards is shown in Figure 4.
In this figure, the CPU on the Mezzanine card is isolated from
the host CPU. The PEX 8608 non-transparent port allows the
two CPUs to be isolated but communicate with each other
through various registers that are designed in the PEX 8608
for that purpose. The host CPU can dynamically re-assign
both the upstream port and the non-transparent port of
PEX 8608 allowing the system to be reconfigured.
Active-Standby Failover Model
The PEX 8608 supports applications requiring dual host, host
failover applications through the non-transparency feature.
Figure 7 illustrates a dual host system with an active and
standby processor configuration.
Figure 4. Control Planes for Large Systems
Embedded Control Planes
The PEX 8608 is well suited for embedded control plane
applications. An example of such application is a packet
processing module, as shown in Figure 5. In this example, the
FPGAs and ASICs implement an x1 PCI Express Interface.
With its high port count, the PEX 8608 can provide
connectivity to a high number of FPGAs and ASICs for a
robust packet processing communications sub-system.
The redundancy of the host and the fabric can be achieved
through many possible configurations using NTB function of
PEX 8608. In the configuration shown below Processor A is
the primary active host of the PCI Express system. Processor
B acts as the backup Host. In the case of a failure on Processor
A, application software is instructed to migrate the PCI
Express system to Processor B. Consequently, Processor B
becomes the active host and Processor A can be replaced as
the backup Host.
Figure 7. Active-Standby Host Mode
Figure 5. Packet Processing Module
Software Usage Model
Interrupt Sources/Events
From a system model viewpoint, each PCI Express port is a
virtual PCI to PCI bridge device and has its own set of
PCI Express configuration registers. It is through the upstream
port that the BIOS or host can configure the other ports using
standard PCI enumeration. The virtual PCI-to-PCI bridges
within the PEX 8608 are compliant to the PCI and PCI
Express system models. The Configuration Space Registers
(CSRs) in a virtual primary/secondary PCI-to-PCI bridge are
accessible by type 0 configuration cycles through the virtual
primary bus interface (matching bus number, device number,
and function number).
The PEX 8608 supports the INTx interrupt message type
(compatible with PCI 2.3 Interrupt signals) or Message
Signaled Interrupts (MSI) when enabled. Interrupts/messages
are generated by PEX 8608 for Hot-Plug events, doorbell
interrupts, baseline error reporting, and advanced error
reporting.
Development Tools
RDK
PLX offers hardware and software tools to enable rapid
customer design activity. These tools consist of a PEX 8608
Rapid Development Kit (RDK), hardware documentation, and
a Software Development Kit (also available at
www.plxtech.com/sdk).
The PEX 8608RDK is a hardware module containing the
PEX 8608 which plugs right into your system (Figure 8). The
PEX 8608RDK hardware module can be installed in a
motherboard, used as a riser card, or configured as a bench-top
board. The PEX 8608RDK can be used to test and validate
customer software. Additionally, it can be used as an
evaluation vehicle for PEX 8608 features and benefits.
SDK
The SDK tool set
includes:
- Linux & Windows
drivers
- C/C++ Source code,
Objects, libraries
- User’s Guides &
Application examples
Windows/Linux Apps
User
Space
PEX API
Kernel
Space
Hardware
PCIe
Driver
NT PnP
Driver
PCI Express Interface
Figure 8. PEX 8608RDK
PLX Technology, Inc.
870 W. Maude Ave.
Sunnyvale, CA 94085 USA
Tel: 1-800-759-3735
Tel: 1-408-774-9060
Fax: 1-408-774-2169
info@plxtech.com
www.plxtech.com
Product Ordering Information
Part Number
Description
PEX8608-BA50BC
PEX8608-BA50BC G
8 Lane, 8 Port PCIe Switch, 196-ball PBGA 15x15mm2 pkg
8 Lane, 8 Port PCIe Switch, 196-ball PBGA 15x15mm2 pkg, Pb-free
PEX 8608 Rapid Development Kit – Add-in Card with x4 Upstream
and Four x1 Downstream
PEX 8608BA-AIC4U1D RDK
Please visit the PLX Web site at http://www.plxtech.com or contact PLX sales at 408-774-9060 for sampling.
© 2009 by PLX Technology, Inc. All rights reserved. PLX and the PLX logo are registered trademarks of PLX Technology, Inc. ExpressLane is a trademark of PLX Technology,
Inc., which may be registered in some jurisdiction. All other product names that appear in this material are for identification purposes only and are acknowledged to be
trademarks or registered trademarks of their respective companies. Information supplied by PLX is believed to be accurate and reliable, but PLX Technology, Inc. assumes no
responsibility for any errors that may appear in this material. PLX Technology, Inc. reserves the right, without notice, to make changes in product design or specification.
PEX8608-SIL-PB-1.2
5/09