Version 0.8 2007
Features
PEX 8648 General Features
o
48-lane, 12-port PCIe Gen2 switch
-
Integrated 5.0 GT/s SerDes
o
27 x 27mm
2
, 676-pin FCBGA package
o
Typical Power: < 7.0 Watts
PEX 8648
PCIe Gen2, 5.0GT/s 48-lane, 12-port PCIe Switch
The
ExpressLane
TM
PEX 8648 device offers PCI Express switching
capability enabling users to add scalable high bandwidth, non-blocking
interconnection to a wide variety of applications including
servers, storage
systems, and communications platforms.
The PEX 8648 is well suited for
fan-out, aggregation, and peer-to-peer
applications.
High Performance & Low Packet Latency
The PEX 8648 architecture supports packet
cut-thru with a maximum
latency of 140ns (x16 to x16).
This, combined with large packet memory
and non-blocking internal switch architecture, provides full line rate on all
ports for performance-hungry applications such as
servers
and
switch
fabrics.
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 2048 bytes, enabling the user to achieve even higher throughput.
Data Integrity
The PEX 8648 provides
end-to-end CRC
(ECRC) protection and
Poison bit
support to enable designs that require
end-to-end data integrity.
PLX also
supports data path parity and memory (RAM) error correction as packets
pass through the switch.
Flexible Register & Port Configuration
The PEX 8648’s 12 ports can be configured to lane widths of x1, x2, x4, x8,
or x16. Flexible buffer allocation, along with the device's
flexible packet
flow control,
maximizes throughput for applications where more traffic
flows in the downstream, rather than upstream, direction. Any port can be
designated as the upstream port, which can be changed dynamically. The
PEX 8648 also
x4
x8
provides several ways
to configure its
registers. The device
can be configured
PEX 8648
PEX 8648
through strapping pins,
I
2
C interface,
host
software, or an optional
3 x8 4 x4
11 x4
serial EEPROM. This
allows for easy debug
x8
x8
during the development
phase, performance
monitoring during the
operation phase, and
PEX 8648
PEX 8648
driver or software
upgrade. Figure 1
shows some of the PEX
2 x8 4 x4
8648’s common port
10 x4
configurations.
Figure 1. Common Port Configurations
PEX 8648 Key Features
o
Standards Compliant
-
PCI Express Base Specification, r2.0
(backwards compatible w/ 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 switch fabric
-
Full line rate on all ports
-
Packet Cut-Thru with 140ns max packet
latency (x16 to x16)
-
2KB Max Payload Size
-
Read Pacing (bandwidth throttling)
-
Dual-Cast
o
Flexible Configuration
-
Ports configurable as x1, x2, x4, x8, x16
-
Registers configurable with strapping
pins, EEPROM, I
2
C, or host software
-
Lane and polarity reversal
-
Compatible with PCIe 1.0a PM
o
Dual-Host & Fail-Over Support
-
Configurable Non-Transparent port
-
Moveable upstream port
-
Crosslink port capability
o
Quality of Service (QoS)
-
Eight traffic classes per port
-
Weighted round-robin source
port arbitration
o
Reliability, Availability, Serviceability
-
3 Hot Plug Ports with native HP Signals
-
All ports hot plug capable thru I
2
C
(Hot Plug Controller on every port)
-
ECRC and Poison bit support
-
Data Path parity
-
Memory (RAM) Error Correction
-
INTA# and FATAL_ERR# signals
-
Advanced Error Reporting
-
Port Status bits and GPIO available
-
Per port error diagnostics
-
Performance Monitoring
•
Per port payload & header counters
-
JTAG AC/DC boundary scan
Preliminary - PLX Confidential
Dual-Host & Failover Support
The PEX 8648 product supports a
Non-Transparent
(NT) Port,
which enables the implementation of
multi-
host systems
in communications, storage, and blade
server applications. The NT port allows 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 (accessible by both CPUs) allow inter-
processor communication (see Figure 2).
Primary
Primary
Host
Host
Secondary
Secondary
Host
Host
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 8648 is
equipped with a hot-plug control/status register to
support hot-plug capability through external logic via the
I
2
C interface.
SerDes Power and Signal Management
The PEX 8648 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 management of the entire system.
Interoperability
The PEX 8648 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, it supports
auto-negotiation, lane
reversal,
and
polarity reversal.
Furthermore, the PEX
8648 is tested 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.
CPU
Blade
Non-Transparent
Port
CPU
Blade
I/O
I/O
NT
PEX 8648
I/O
Figure 2. Non-Transparent Port
Dual Cast
The PEX 8648 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 dual-graphics, storage, security, and
redundant applications.
Read Pacing
The Read Pacing feature allows users to throttle the
amount of read requests being made by downstream
devices. When 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.
Hot Plug for High Availability
Hot plug capability allows users to replace hardware
modules and perform maintenance without powering
down the system. The PEX 8648 hot plug capability
feature makes it suitable for
High Availability (HA)
applications.
Three downstream ports include a
Standard Hot Plug Controller. If the PEX 8648 is used in
Applications
Suitable for
host-centric
as well as
peer-to-peer traffic
patterns,
the PEX 8648 can be configured for a wide
variety of form factors and applications.
Host Centric Fan-out
The PEX 8648, with its symmetric or asymmetric lane
configuration capability, allows user-specific tuning to a
variety of host-centric applications. Figure 3 shows a
typical
server
design where the root complex provides a
PCI Express link that needs to be expanded to a larger
number of smaller ports for a variety of I/O functions. In
this example, the PEX 8648 has a 16-lane upstream port,
and five downstream ports using x8 and x4 links.
The PEX 8648 can also be used to create PCIe Gen1 (2.5
Gbps) ports. The PEX 8648 is backwards compatible
with PCIe Gen1 devices. Therefore, the PEX 8648
enables a Gen 2 native Chip Set to fan-out to Gen 1
endpoints. In Figure 3, the PCIe slots connected to the
PEX 8648’s downstream ports can be populated with
either PCIe Gen1 or PCIe Gen 2 devices. Conversely,
the PEX 8648 can also be used to create Gen 2 ports on
a Gen 1 native Chip Set in the same fashion.
Preliminary - PLX Confidential
CPU
CPU
CPU
CPU
PEX 8648 utilizes its NT port to isolate the hosts on the
switch fabrics and the remaining 10 downstream ports
on each switch are used to fan-out to the 20 AMC blades
(or 10 AMC Carrier Modules).
Memory
10-20 AMC or 10 AMC
Carrier Modules
Fabric
To
Backplane
CPU
Chipset
Endpoint
x16
x16
x16
PEX 8648
Endpoint
PEX 8648
x8
x8
x8
x4
x4
NT
PEX 8648
To other
Fabric
PCIe Gen1 or PCIe Gen2 slots
Figure 3. Fan-in/out Usage
Communications Systems
The PEX 8648 can also be utilized in communications
applications. Figure 4 shows a PEX 8648 being used in a
router to connect multiple endpoints in a line card to the
control module using PowerPC. The link-widths for each
module can be configured as required. The peer-to-peer
communication feature of the PEX 8648 allows the
endpoints to communicate with each other without any
intervention or management by the host.
Figure 5. ATCA/MicroTCA Backplane Usage
Fail-Over Storage Systems with Dual Cast
The PEX 8648’s Dual Cast feature proves to be very
useful in storage systems. In the example shown in
Figure 6, the Dual Cast feature enables the PEX 8648 to
copy data coming from the host to two downstream ports
(see yellow traffic patterns) in one transaction as
opposed to having to execute two separate transactions
to send data to the redundant chassis. By offloading the
task of backing up data onto the secondary system,
processor and system performance is enhanced. The
PEX 8648’s NT port is used to isolate the backup system
from the primary system.
CPU
CPU
CPU
CPU
CPU
CPU
CPU
Control
Module
PowerPC
Memory
x8 or x4
Backup
System
End
Point
PEX 8648
End
Point
End
Point
End
Point
End
Point
End
Point
CPU
Chipset
x8
Memory
Chipset
x8
Memory
x8
NT
Line Card
PEX 8648
All
x8s
PEX 8648
All
x8s
Figure 4. Router Usage
Backplane Communication
With 48 lanes and 12 ports, the PEX 8648 is well suited
for backplane applications requiring high connectivity (a
large number of ports). Figure 5 represents an ATCA or
MicroTCA backplane application with two switch fabric
blades and multiple AMC blades. In this example, two
PEX 8648s provide peer-to-peer data exchange for up to
20 AMC blades connecting to the switch fabric. The
NT
NT
NT
NT
PEX 8616
x4
x4
FC
FC
PEX 8616
x4
x4
FC
FC
PEX 8616
x4
x4
FC
FC
PEX 8616
x4
x4
FC
FC
8 Disk Chassis
8 Disk Chassis
8 Disk Chassis
8 Disk Chassis
Figure 6. Dual Cast in Storage Systems
Preliminary - PLX Confidential
Software Usage Model
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 8648 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).
Interrupt Sources/Events
The PEX 8648 switch 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 8648 for hot
plug events, doorbell interrupts, baseline error reporting,
and advanced error reporting.
Development Tools
PLX offers hardware and software tools to enable rapid
customer design activity. These tools consist of a
hardware module (PEX 8648 RDK), hardware
documentation (available at
www.plxtech.com),
and a
Software Development Kit (also available at
www.plxtech.com).
ExpressLane
PEX 8648 RDK
The PEX 8648 RDK is a hardware module containing
the PEX 8648 which plugs right into your system. The
PEX 8648 RDK can be used to test and validate
customer software, or used as an evaluation vehicle for
PEX 8648 features and benefits. The PEX 8648 RDK
provides everything that a user needs to get their
hardware and software development started. For more
information, please refer to the PEX 8648 RDK Product
Brief.
Software Development Kit (SDK)
PLX’s Software Development Kit is available for
download at
www.plxtech.com/sdk.
The software
development kit includes drivers, source code, and GUI
interfaces to aid in configuring and debugging the PEX
8648. For more information, please refer to the PEX
8648 RDK Product Brief.
Product Ordering Information
PLX Technology, Inc.
870 Maude Ave.
Sunnyvale, CA 94085 USA
Tel: 1-800-759-3735
Tel: 1-408-774-9060
Fax: 1-408-774-2169
Email: info@plxtech.com
Web Site: www.plxtech.com
Part Number
PEX8648-AA50BC G
PEX8648-AA RDK
Description
48-Lane, 12-Port PCI Express Switch, Pb-Free (27x27mm
2
)
PEX 8648 Rapid Development Kit
Please visit the PLX Web site at
http://www.plxtech.com
or contact PLX sales at 408-774-9060 for sampling.
© 2007 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.
PEX8648-SIL-PB-P1-0.8
09/07
Preliminary - PLX Confidential
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