Version 1.7 2007
.
PEX 8508
Flexible & Versatile PCI Express® Switch
Features
PEX 8508 General Features
o 8-lane PCI Express switch
- Integrated SerDes
o Up to five configurable ports
o 19mm x 19mm, 296-ball PBGA
package
Multi-purpose and Feature Rich PCI Express Switch Family
o Typical Power: 1.6 Watts
The ExpressLane™ PEX 8508 device offers PCI Express switching capability
enabling users to add scalable high bandwidth, non-blocking interconnection to a
wide variety of applications including intelligent network interface cards, office
automation products, mezzanine cards, servers, storage systems,
communications platforms, laptop docking stations, and embedded-control
products. The PEX 8508 switch can be used as a fan-out or aggregation type
switch, and is equally well-suited to peer-to-peer switching applications.
PEX 8508 Key Features
o Standards Compliant
- PCI Express Base Specification, r1.1
- Standard SHPC Specification, r1.1
(hot-plug)
o High Performance
- Non-blocking internal architecture
- Full line rate on all ports
- Cut-Thru latency: 150ns
o Non-Transparent Bridging
- Configurable Non-Transparent port
for Multi-Host or Intelligent I/O
Support
o Flexible Configuration
- Five highly flexible & configurable
ports (x1, x2, or x4)
Highly Flexible Port Configurations
The PEX 8508 offers highly configurable ports. There are a maximum of five ports
and eight lanes that can be configured to any legal width from x1 to x4, in any
combination to support your specific bandwidth needs. The ports can be symmetric
(each port having the same lane width) or asymmetric (ports having different lane
widths). If you can think of a port/lane combination, you can configure it! Any of
the ports can be designated as the upstream port, and you can even dynamically
change the upstream port.
- 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, L2 and L3
- Device states: D0 and D3hot
- Vaux, WAKE#, Beacon support
o Spread Spectrum Clock
- Dual clock domain
o Quality of Service (QoS)
- Two Virtual Channels per port
- Eight Traffic Classes per port
- Fixed and Round-Robin Virtual
Channel Port Arbitration
End-to-end Packet Integrity
The PEX 8508 provides end-to-end CRC protection (ECRC) and Poison bit support
to enable designs that require guaranteed error-free packets. These features are
optional in the PCI Express specification, but PLX provides them across its entire
ExpressLane switch product line.
Non-Transparent “Bridging” in a PCI Express Switch
The PEX 8508 supports full non-transparent bridging (NTB) functionality to allow
implementation of multi-host systems and intelligent I/O modules in applications
such as intelligent adapter cards, processor isolation, and office automation. To
ensure quick product migration, the non-transparency features are implemented in
the same fashion as in standard PCI applications.
Non-transparent bridges allow systems to isolate 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.
o Reliability, Availability, Serviceability
- 5 Standard Hot-Plug Controllers
- Upstream port as hot-plug client
- Transaction Layer end-to-end CRC
- Poison bit
Two Virtual Channels
- Advanced Error Reporting
- Lane Status bits and GPO available
- Per port error diagnostics
• Bad DLLPs
• Bad TLPs
• CRC errors
The PEX 8508 switch supports two full-featured Virtual Channels (VCs) and eight
Traffic Classes (TCs). The mapping of Traffic Classes to port-specific Virtual
Channels allows for different mappings for different ports. In addition, the devices
offer user-selectable Virtual Channel arbitration algorithms to enable users to fine
tune the Quality of Service (QoS) required for a specific application.
- JTAG boundary scan
- Fatal Error out-of-band signal option
Low Power with Granular SerDes Control
The PEX 8508 provides low power capability that is compliant with the PCI Express
power management specification. The SerDes physical links can be turned off when
unused for even lower power. Support for Vaux, Wake#, and Beacon allows D3cold
operation and is crucial in such applications as docking stations.
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